H. Terry Fortune (Deceased)

151. “Quantum phase transitions and band mixing in ¹³⁵Ba”, A. J. Majarshin, Yan-An Luo, Feng Pan, H. T. Fortune, Yu Zhang and J. P. Draayer, J. Phys. G: Nucl. Part. Phys. 48, 125107 (2021)-published 10 November 2021.

Quantum phase transitions and band-mixing phenomena are considered within the framework of a two-state boson–fermion model for the odd-mass ¹³⁵Ba nucleus. The purpose of the study is to further explore the nature of the interplay between these modalities within the framework of an even–even boson core described by an IBM Hamiltonian coupled to a j = 3/2 fermion as a function of the strength of the coupling constant that links the boson and fermion pictures. The results show that excitation energies and the known E2 strengths of ¹³⁵Ba are sensitive to the strength of the coupling constant, with a best fit to known experimental results yielding results that lie close to those of the recently proposed E(5/4) model.

150. “Structure of rotational bands in ¹⁰⁹Rh”, A. J. Majarshin, Yan-An Luo, Feng Pan, and H. T. Fortune, Phys. Rev. C 104, 014321 (2021) - Published 28 July 2021.

Rotational bands in ¹⁰⁹Rh are investigated in a simple model and in the interacting boson-fermion model. We have developed a solvable extended transitional Hamiltonian by adding a two-configuration mixing term. Results suggest that ¹⁰⁹Rh is a good candidate for triaxiality and shape coexistence. Mixing between 3/2⁺ states with K=1/2 and 3/2 is found to be weak, as evidenced by the E2 strengths.

149. “Possible 3⁺ state in ¹²Be from the ¹¹Be(d,p) reaction”, H. T. Fortune, Phys. Rev. C 104, 014314 (2021) - Published 16 July 2021.

A simple calculation indicates that the observed energy and width of a state at 6.02(15) MeV in ¹²Be, populated in the ¹¹Be(d,p) reaction, are consistent with expectation for the first 3⁺ state with dominant configuration ¹⁰Be(ground state) ×(2s1/2)(1d5/2).

148. “Methods of calculating widths for decays to unbound states”, H. T. Fortune. Nucl. Phys. A  1014, 122249 (2021), published 9 June 2021.

I describe various techniques for computing widths for decay to daughter states that are themselves unbound. I present examples of their similarities and differences.

147. “Coexistence and configuration mixing in ¹¹²Cd”, H. T. Fortune. Nucl. Phys. A 1014, 122233 (2021), published 28 May 2021.

I have performed a two-state mixing analysis between so-called rotational intruder 0⁺, 2⁺ and yrast 0⁺, 2⁺ states in ¹¹²Cd, fitting E2 transition matrix elements to obtain mixing amplitudes and matrix elements connecting basis states. Mixing is found to be small for both 0⁺ and 2⁺ states. Of two possible solutions, one provides a 0⁺ mixing amplitude of 0.251– identical to the one derived years ago from 2n transfer

146. “2n transfer and E2 strengths in ¹⁵⁴Sm”, H. T. Fortune, Phys. Rev. C 103, 054316 (2021) - Published 20 May 2021.

Two separate analyses of E2 strengths among the first two bands in ¹⁵⁴Sm are consistent. They indicate that mixing is small and decreases with increasing J.

145. “Observation of the near-threshold intruder 0⁻ resonance in ¹²Be”, J. Chen et al., Phys. Rev. C 103, L031302 (2021) - Published 17 March 2021.

A resonant state at 3.21_−0.04^+0.12 MeV, located just above the one-neutron separation threshold, was observed for the first time in ¹²Be from the ¹¹Be(d,p) ¹²Be one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of 0⁻ according to the systematics of the level scheme of the N=8 isotones and decay-width analysis. Gamow coupled-channel and Gamow shell-model calculations show the importance of the continuum coupling, which dramatically influences the excitation energy and ordering of low-lying states. Various exotic structures associated with cross-shell intruding configurations in ¹²Be and in its isotonic nucleus ¹¹Li are comparably discussed.

144. “Further examination of a possible vibrational-rotational index”, H. T. Fortune. Nucl. Phys. A 1010, 122188 (2021), published 16 March 2021.

For other, mostly non-coexistence nuclei, I have examined a dimensionless ratio of E2 strengths that has been demonstrated to display a double-peaked frequency distribution for coexistence nuclei, with a void of points near R = 0.20. Results indicate that the lower peak remains, as does a deep minimum near R = 0.20, but that ratios above R = 0.20 are more widely spread for nuclei not known to exhibit coexistence.

143. “Nuclear structure and band mixing in ¹⁹⁴Pt”, A. Jalili Majarshin, Yan-An Luo, Feng Pan, H. T. Fortune, and Jerry P. Draayer, Phys. Rev. C 103, 024317 (2021) - Published 16 February 2021.

We introduce a two-particle, two-hole mixed configuration scheme to fit E2 strengths for the 0↔2, 2↔4, and 4↔6 transitions in ¹⁹⁴Pt. The interaction includes two sets of pairing operators, {S_±(t),S₀(t)} (t=s,d). Solutions within this framework are used to analyze energy spectra, E2 transitions, and band-mixing features of the model. The results confirm that mixing is small and similar for J=2, 4, and 6, with the calculated energies and transition matrix elements in excellent agreement with experimental data.

142. “Spherical-deformed mixing in ⁹⁴Zr”, H. T. Fortune, Phys. Rev. C 103, 024308 (2021) - Published 5 February 2021.

I have applied a simple two-state mixing model to E2 strengths from a recent ⁹⁴Zr (n,n′γ) experiment in order to obtain the mixing amplitudes between spherical and deformed basis states in ⁹⁴Zr. The fits also provide the transition matrix elements connecting the basis states.

141. “Proposed new classification among coexistence nuclei”, H. T. Fortune. Nucl. Phys. A 1004, 122063 (2020), published 26 October 2020.

I propose a new classification of coexistence nuclei that involves E2 transition matrix elements connecting the ground state, 2₁ and 2₂ (or 2₃) states. A dimensionless ratio, based only on experimental information, is defined, and most coexistence nuclei are found to lie within one of only two narrow bands of this ratio.

140. “Proton widths and spectroscopic factors in ¹⁹F at E_x = 8–11 MeV”, H. T. Fortune, Phys. Rev. C 102, 024333 (2020) - Published 28 August 2020.

For states of ¹⁹F from E_x = 8.1 to 10.9 MeV, I have examined the proton spectroscopic factors from the reaction ¹⁸O(d,n) and compared them with spectroscopic factors computed from the proton widths. Even though the widths cover a range greater than a factor 10⁵, the two sets of spectroscopic factors agree to within about a factor of 2.

139. “Coexistence in ⁷²Kr”, H. T. Fortune, Phys. Rev. C 102, 024334 (2020) - Published 28 August 2020.

I have applied a simple two-state mixing model to E2 strengths among low-lying states in ⁷²Kr. Solutions are found with basis states in⁷²Kr similar to those in ⁷⁴Kr. As expected, the amount of the more collective basis state in the yrast states increases with J for J=0, 2, and 4.

138. “Properties of excited 0⁺ states in ¹⁴C and ¹⁴O”, H. T. Fortune, Phys. Rev. C 102, 014309 (2020) - Published 13 July 2020.

I have computed expected energies and widths of excited 0⁺ states in ¹⁴O, using experimental information from ¹⁴C and a variety of wave functions. Agreement for the 0₂ state is fair, but my calculations do not support a recent suggestion that a previously unknown state unresolved from the second 2⁺ state might be the 0₃ state.

137. “Comparison of the ⁹Be(t,p)¹¹Be and ⁹Be(¹⁸O,¹⁶O)¹¹Be reactions”, H. T. Fortune, Phys. Rev. C 101, 024314 (2020) - Published 27 February 2020.

Relative to their population in a recent investigation of the ⁹Be(¹⁸O,¹⁶O)¹¹Be reaction, the first two (sd)² states of ¹¹Be were considerably stronger (by factors of 2–3) in an earlier ⁹Be(t,p) experiment. Comparison with other results suggests the presence of at least two states near 5.9 MeV, populated with different selectivity in different reactions.

136. “Coexistence and 2n transfer among Mo nuclei”, H. T. Fortune, Phys. Rev. C 100, 064322 (2019) - Published 30 December 2019.

I have analyzed experimental 2n transfer data for ground and first-excited 0⁺ states in even ^92–100Mo nuclei, using a generalized coexistence model. Output of the analysis is the mixing intensity for each nucleus in terms of a dimensionless parameter R, which is limited to a narrow range. Throughout the allowed range, the mixing is found to be monotonic in A, and is largest in ¹⁰⁰Mo.

135. “Similarities and differences in ¹¹⁶Sn and ¹¹⁴Cd”, H. T. Fortune, Phys. Rev. C 100, 054328 (2019) - Published 22 November 2019.

I have compared the proton closed-shell (Z=50) nucleus ¹¹⁶Sn with its neighbor ¹¹⁴Cd, which has Z=48. In both energies and E2 strengths, both large similarities and major differences are pointed out. I have estimated mixing of the lowest 0⁺ and 2⁺ states with the sum of second and third states of each J^π. Mixing is much larger in ¹¹⁴Cd than in ¹¹⁶Sn.

134. “2p decays of ¹²O excited states”, H. T. Fortune, Phys. Rev. C 100, 054318 (2019) - Published 14 November 2019.

In ¹²O, the 2⁺ state whose dominant configuration is ¹⁰C(2⁺)×π(sd)²₀ should be populated in neutron removal from ¹³O, and its primary decay is via 2p emission to the 2⁺ state of ¹⁰C. My calculations predict that most of the events near E_2p = 3.5 MeV in a recent ¹²O → ¹⁰C +2p experiment represent decays to the 2⁺ state.

133. “Coexistence and 2′→2₁ E2 strengths”, H. T. Fortune, Phys. Rev. C 100, 054305 (2019) - Published 5 November 2019.

I have used parameters previously determined from a simple mixing analysis of 0 ↔ 2 transition strengths in several nuclei to compute E2 transition matrix elements for the 2₂ (or 2₃, as determined by the experimenters) →2₁ transition. Agreement with experimental E2 transition matrix elements is reasonable.

132. “Coexistence and mixing in ^182,184Hg”, H. T. Fortune, Phys. Rev. C 100, 044303 (2019) - Published 4 October 2019.

I have used a simple two-state mixing model to analyze 0 ↔ 2 transition matrix elements in ^182,184Hg. Fits provide 0⁺ and 2⁺ mixing in both nuclei, and values of basis-state E2 matrix elements. I agree with previous work that the ground state contains most of the less-collective basis state, but the converse is true for the 2⁺. It turns out that the potential mixing matrix elements are not independent of J, as is commonly assumed. I also include an analysis with newly revised matrix elements.

131. “Coexistence and 2n transfer in even Zr nuclei”, H. T. Fortune, Phys. Rev. C 100, 034303 (2019) - Published 6 September 2019.

In a simple coexistence model, I have examined 2n transfer ratios of 0⁺ states in even Zr nuclei. Results indicate that mixing is small in ⁹⁶Zr, but larger and nearly equal in ^{92, 94}Zr, with ⁹⁰Zr slightly larger. The ⁹⁶Zr result is consistent with earlier analyses of E2 strengths.

130. “Population of ¹¹O^∗ in two-neutron removal from ¹³O”, H. T. Fortune, Phys. Rev. C 100, 024332 (2019) - Published 27 August 2019.

I have used a simple model to estimate the relative populations expected for the ground state (g.s.) and three excited states of ¹¹O in 2n removal from ¹³O. Results are ratios exc./g.s. of at most a few percent for each excited state, compared to ratios near unity suggested in a recent experiment involving ¹¹O.

129. “Mirror states in ⁹Li and ⁹C”, H. T. Fortune, Phys. Rev. C 100, 014321 (2019) - Published 26 July 2019.

I have used a potential model to examine mirror states in ⁹Li and ⁹C. The mirror energy difference and observed widths of the supposed 7/2⁻ states are consistent with dominant parentage to the 3⁺ excited state of ⁸Li and ⁸B. The newly reported s-wave resonance at 4.3 MeV in ⁹C should have a mirror near E_x = 5.39(38) MeV in ⁹Li.

128. “Wave functions of 0⁺ states in ¹²Be”, H. T. Fortune, Phys. Rev. C 99, 064314 (2019) - Published 11 June 2019.

New proposed orbital occupancies for 0⁺ states in ¹²Be are at variance with those normally in use. I have investigated implications for single- particle energies, ¹²Be/¹²O mass difference, cross sections for the reaction ¹⁰Be(t,p), B(GT) from ¹²B, and other observables.

127. “T mixing and decay widths of first two 1⁻ states in ¹⁰B”, H. T. Fortune, Phys. Rev. C 99, 064305 (2019) - Published 4 June 2019.

For the isospin-mixed 1⁻ states in ¹⁰B, widths for deuteron and α decays provide an independent estimate of the amount of isospin mixing, which is consistent with results from γ decays. Analysis provides two solutions for the proton spectroscopic factors of the pure T = 0 and 1 states.

126. “Coexistence and mixing in ⁷⁶Se”, H. T. Fortune, Phys. Rev. C 99, 054320 (2019) - Published 17 May 2019.

A simple two-state mixing model has been applied to the 0⁺, 2⁺, and 4⁺ states in the first two 0⁺ bands in ⁷⁶Se. The first two 0⁺ states are found to be almost maximally mixed. The excited basis-state band has the energy and E2 strengths characteristic of a K = 0 rotational band, but the lower basis-state band does not. The e band is significantly more collective than the g band.

125. “Energy and width of ¹¹O(g.s.)”, H. T. Fortune, Phys. Rev. C 99, 051302(R) (2019) - Published 14 May 2019.

I have used a potential model and a convolution procedure to compute energy-dependent widths for simultaneous ¹¹O(g.s.) → ⁹C+2p decay. A Breit-Wigner shape calculated with those widths provides excellent agreement with recent experimental data.

124.  2n decays of 16Be,

Phys. Rev. C 99, 044318 (2019) - Published 29 April 2019.

I have estimated the decay width of Be16 for a variety of decay mechanisms: 2n cluster decay, sequential decay through the known 5/2+ state of Be15, and sequential decay through a hypothetical 1/2+ state in Be15. Only the cluster decay width is comparable to the reported experimental width.

123. Formation and decay of an excited state in 11Li,

Nuclear Physics A, 987, 29 (2019). Available online 15 April 2019.

I address the formation and decay of an excited state in 11Li that may be the so-called soft dipole. I discuss why this soft dipole should be populated very weakly in two-proton removal from 13B. I have used a potential model to estimate its width for 2n cluster decay, which turns out to be well within the experimental limit. After correcting the data for efficiency, a simple Breit-Wigner curve, convoluted with the experimental resolution widths, is found to provide an excellent fit.

122. Ratios of matter radii for isotones of light nuclei

Phys. Rev. C 99, 034309 (2019) - Published 11 March 2019.

I have compared matter radii for nuclei having the same neutron number but differing by one or two in proton number. The ratios reveal features that are less apparent in the actual matter radii.

121.  2n transfer and E2 strengths in 150, 152Sm,

Nuclear Physics A, 984, 1 (2019). Available online 17 January 2019.

In a simple coexistence model, I have examined 2n transfer ratios of 0+ states in even Sm nuclei. I have performed a unified analysis of 2n and E2 data in 150, 152Sm. Results are in good agreement with the data.

120. Update on energies and widths in 13Be

Phys. Rev. C 99, 014304 (2019) - Published 7 January 2019.

I have compared new experimental information on resonances in Be13 with results of theoretical calculations. For the 1/2+ resonance at 0.86 MeV, the reported width of 1.70(15) MeV is considerably larger than the single-particle limit of 1.3 MeV. For the first 5/2+, the calculated width and 2+ branching ratio for neutron decay are both in rough agreement with the data. I discuss the possibility that events from decay of the second 5/2+ to Be12(2+) could contribute to the 0.86-MeV peak. If the 4.0-MeV resonance is indeed 3/2+, then its width should be considerably larger than reported.

119. Band mixing in 74, 76, 78Kr

Eur. Phys. J. A 54, 229 (2018). Published online: 24 December 2018.

A simple two-state mixing model has been applied to members of the two rotational bands containing the two lowest 0+ states in 74,76,78Kr. For each even angular momentum J, two physical states are taken to be linear combinations of basis states Jg and Je. Mixing amplitudes are varied in order to reproduce E2 transition matrix elements. Unique solutions are found for the 0+ and 2+ mixing in all three cases, and for the E2 matrix elements connecting the basis states. The basis-state band containing basis state 0g is found to be much more collective than the one containing 0e in 74,78Kr, and somewhat more collective in 76Kr. From the fit, the amount of basis state Je in the lower of the two physical J states decreases very rapidly with increasing J. The 2+ wave functions from the fit are used to compute matrix elements for 4 ↔ 2 transitions, some of which are unknown. A sign discrepancy is noted for the 22 → 41 transition matrix element in 74Kr.

118. Band mixing and structure of 106,108Pd

Phys. Rev. C 98, 064303 (2018) - Published 3 December 2018.

A simple two-state mixing model has been applied to members of the two lowest 0+rotational bands in Pd106,108. Unique solutions are found for the 0+ and 2+ mixing in both cases, and for the E2 matrix elements connecting the basis states. The lower basis-state band is found to be somewhat more collective than the second one. Results indicate that Pd108 is slightly more collective than Pd106. In Pd106, The 2+ wave functions from the fit are used to compute matrix elements for 4 ↔ 2 transitions, one of which is unknown.

117. Decays of 15Be(5/2+)

Phys. Rev. C 98, 054317 (2018) - Published 26 November 2018.

I have computed spectroscopic factors S and single-particle widths Γsp, and hence expected decay widths Γcalc=SΓsp for decay of the lowest 5/2+ state of Be15 to the ground state and first 2+ state of Be14. Results indicate that decay to the 2+ state should be appreciable.

116. Band mixing in 154Gd

Eur. Phys. J. A 54, 178 (2018). Published online: 24 October 2018.

I have applied a simple two-state mixing model to members of the first two rotational bands in 154Gd. Resulting mixing amplitudes are similar for 0+, 2+, 4+, and 6+, with mixing decreasing slightly with increasing J. The analysis indicates that 154Gd is very similar to 152Sm for these first two bands. Results suggest that the larger of the two experimental strengths that are available for the 22 → 02 transition in 154Gd is the correct one.

115. Configuration mixing in 12,14O and the 14O(p, t) reaction,

Physics Letters B 785, 1 (2018). Pub 10 October 2018,

In two-neutron pickup from 14O, the calculated cross-section ratio for the first two 0+ states of 12O depends on the configuration mixing in these two states, and on the amount of core excitation in the ground state (g.s.) of 14O. Using mirror symmetry and 12Be wave functions that are reasonably well known, I have calculated this ratio as a function of the core excitation in 14O(g.s.). Results suggest that the excited-state cross section from a recent measurement is too large.

114. Competing 1n and 2n decays in 12Be

Phys. Rev. C 98, 041301(R) (2018) - Published 1 October 2018.

I have estimated widths for 2n decay for all positive-parity states expected in the region of 4.0–5.5 MeV in Be12. Results indicate that 2n decay could compete with 1n decay for one of the states—the fourth 2+ that is likely to be the state observed in one-proton removal from B13.

113. Proton removal from 13B to negative-parity states of 12Be

Phys. Rev. C 98, 024322 (2018) - Published 30 August 2018.

I have estimated the amount of p−shell→(sd)2 core excitation in B13 that involves an sd-shell proton, and then the spectroscopic factors for proton removal from B13 to negative-parity states of Be12. Results are S∼10−2, indicating that these states are unlikely to be populated in that reaction.

112. Matter radii of 16−23N

Phys. Rev. C 98, 024307 (2018) - Published 15 August 2018.

I have used a simple model to compute matter radii for N16–23, paying special attention to the configurations of the valence neutron(s). I compare results with recent predictions and with earlier matter radii extracted from measurements of interaction cross sections. The present calculations are closer to the experimental radii than any of the results from the other procedures.

111. Classification of 20F states below 4.4 MeV

Phys. Rev. C 98, 014314 (2018) - Published 11 July 2018.

Angle-integrated cross sections and forward/backward ratios for the reaction O18(He3,p)F20 have been combined with existing information in order to classify F20states up to 4.4 MeV excitation. Experimental counterparts are now known for all 13 (sd)4shell-model states in this region.

110. Energies and widths in 11N

Phys. Rev. C 98, 014307 (2018) - Published 5 July 2018.

Using experimental information from Be11 and a simple potential model, I have computed energies and widths expected for several resonances in N11. The conclusion is that two or three expected resonances have never been observed.

109. Matter radii and configuration mixing in 15-19C,

Eur. Phys. J. A 54, 73 (2018). Published online: 14 May 2018.

I present new calculations of matter radii for 15–19C, with a variety of mixed configurations. Results are compared with previous and new matter radii deduced from cross sections.

108. Update on matter radii of 17−24O

Phys. Rev. C 97, 054309 (2018) - Published 9 May 2018.

The appearance of new theoretical papers concerning matter radii of neutron-rich oxygen nuclei has prompted a return to this problem. New results provide no better agreement with experimental values than did previous calculations with a simple model. I maintain that there is no reason to adjust the O22 core in the O24 nucleus, and the case of O24 should be reexamined experimentally.

107. The 1d5/2 single-particle state and widths in 14O and 15,16F

Phys. Rev. C 97, 044314 (2018) - Published 17 April 2018.

I have examined spectroscopic factors for predominantly 1d5/2 single-particle states in isospin multiplets having A=14−16. Results indicate a serious problem with the width of the 5/2+ resonance in F15. Calculations provide recommended widths in O14 and F16.

106. 24Na at Ex=4.7−5.9MeV from 22Ne(3He,p)

Phys. Rev. C 97, 044307 (2018) - Published 12 April 2018.

Abstract. Analysis of data from the Ne22(He3,p) Na24 reaction has been extended to include 18 angular distributions for states between 4.7 and 5.9 MeV. A distorted-wave Born-approximation analysis allows the determination of ℓ value(s) for most of them. Results for Jπ are compared with previous information. In general, agreement is good. Some apparent disagreements between current and past results are indicative of population of a different state in this reaction than the nearby one listed in the compilation.

105. Structure of exotic light nuclei: Z = 2, 3, 4,

Eur. Phys. J. A 54, 51 (2018). Published online: 28 March 2018.

I examine the history and current state of knowledge of the structure of so-called “exotic” light nuclei with Z = 2–4, from 7He to 16Be. I review the available experimental information and the models that have been applied to these nuclei. I pay particular attention to the interplay among energies, widths (or strengths), and microscopic structure. Throughout the presentation, I focus on a unified description of these nuclei. I point out contradictions within the data, and I suggest experiments that are still needed.

104. Mirror energy differences of 2s1/2, 1d5/2, and 1f7/2 states

Phys. Rev. C 97, 034301 (2018) - Published 1 March 2018

I have examined mirror energy differences between 2s1/2, 1d5/2, and 1f7/2 single-particle states in neutron-excess light nuclei and their proton-excess mirrors. I expand on the earlier 2s1/2 treatment. For 1d5/2, I find that 11 such cases can be fitted by a simple expression, which I then use to compute the energies of other 1d5/2 states. Agreement with experimental values is good. Agreement is found to be even better for 1f7/2 states.

103. Resonances in 16B

Phys. Rev. C 97, 024328 (2018) - Published 22 February 2018.

Using information from nearby nuclei and a simple model, I estimate that the lowest resonance in B16 should have Jπ=2− and the structure C17(1/2+)×(p3/2)−1, and not 0−, as previously supposed. If the 2− is not the ground state, it should be very close in energy.

102. B(E2;5/2−→1/2−) in 17N and 17Ne

Phys. Rev. C 97, 014308 (2018) - Published 17 January 2018.

A simple model of E2 strengths previously applied to several neutron-excess light nuclei is used to investigate the 1/2−→5/2− transition strength in Ne17, with the aid of mirror symmetry. The calculation is found to be in good agreement with results of a recent measurement and emphasizes a likely problem with the same transition in N17.

101. Sequential decay of 16Ne(2+1)

Phys. Rev. C 96, 064313 (2017) - Published 18 December 2017.

I have computed the width for sequential 2p decay of the first 2+ state of Ne16, using a potential model and convolution over the first two resonances in F15. The result is 83 keV, somewhat larger than a recent computed value of 56 keV and smaller than the experimental value of 150(50) keV.

100. Widths of 26P(1+) and mass of 26P(g.s.)

Phys. Rev. C 96, 054329 (2017) - Published 29 November 2017.

For the 1+ first-excited state of P26, the lifetime and the upper limit on the proton width have been combined with shell-model spectroscopic factors to place an upper limit on the proton single-particle (sp) width. With a potential model, this limit on sp width allows an upper limit on the 1+ resonance energy of Er<124keV. Combining with the known 1+excitation energy provides a limit on the proton separation energy of P26(g.s.) of Sp>40keV, considerably better than a recent result of Sp>−135keV from a similar procedure that used R-matrix sp widths.

99. Narrow resonances in 11N and 15F

Nuclear Physics A 968, 342 (2017). Available online 12 September 2017.
 
I present calculations for an expected narrow resonance in 11N at about 4.79 MeV, with a total proton decay width of about 74 keV, all but 2 keV of which is to the 2+ state of 10C. I compare with a similar situation in 15F, which has been long predicted and recently observed.

98. Mass excesses of 21–24Si and 24S

Phys. Rev. C 96, 034304 (2017) - Published 5 September 2017.

I have used a recent parametrization of mirror energy differences to predict two-proton separation energies for Si21−24 and S24. Results are in good agreement with experimental values for Si22,24.

97. Widths of low-lying levels of 17Na

Phys. Rev. C 96, 024320 (2017) - Published 24 August 2017.

I have used a potential model and results from an earlier shell-model calculation to compute expected widths for decays of the first three states of Na17. I compare them with a recent experiment that observed a large peak near the region of the predicted 3/2+ and 5/2+ states.

96. 2p decays of 11O

Phys. Rev. C 96, 014317 (2017) - Published 26 July 2017.

In a potential model, I have estimated decay widths for O11 to C9+2p for sequential decay through N10 resonances and by simultaneous 2p (He2) decay by integrating over the relevant energy profiles. Results indicate that sequential decays through positive-parity resonances are only slightly smaller than those through negative-parity resonances. Simultaneous decay is predicted to be larger than sequential.

95.Nature of first two rotational bands in 152Sm

Nuclear Physics A 966, 47 (2017). Available online 6 June 2017.

I have applied a simple two-state mixing model to members of the first two rotational bands in 152Sm. Resulting mixing amplitudes are similar for 0+, 2+, and 4+. The lower basis-state band is found to be only slightly more collective than the second one. The results indicate that the un-mixed bands have the character of K="0 rotational bands.

94. Shape coexistence and mixing in 96Zr

Phys. Rev. C 95, 054313 (2017) - Published 17 May 2017.

I have performed a reanalysis of mixing between the first two 0+ and 2+ states in Zr96. My mixing amplitude for the 0+ states is about three times a recent value, although both are small. My mixing is consistent with the E0 strength connecting the two 0+ states, whereas the earlier mixing gives an E0 strength that is too small by an order of magnitude.

93.  Coexistence and B(E2)'s in 42Ca

Nucl. Phys. A 962, 1 (2017).  Published June 2017.

New data have just appeared for Coulomb excitation of 42Ca, providing E2 transition matrix elements connecting several low-lying states. I have applied a simple two-state mixing model to the lowest two 0+,2+, and 4+ states in order to fit the experimental matrix elements. Results indicate that the 0+ and 4+ states are nearly pure, whereas the 2+ states are strongly mixed. My excited band is found to be about 3.6 times more collective than the ground band.

92.  Mixing of higher-J states in 72Ge

Phys. Rev. C 95, 044317 (2017) - Published 20 April 2017

Using published E2 matrix elements, I have determined the amount of mixing between the lowest two 2+, 4+, and 6+ states in 72Ge. I also extracted the E2 strengths connecting the unmixed states. One set of basis states is found to form an excellent K=0 rotational band, and the other is found to form a K=2 band.

91.  Isospin mixing of 2+ states in 14N

Phys. Rev. C 95, 024325 (2017) - Published 27 February 2017

I have investigated the possibility that the near vanishing of the proton strength of the 9.17-MeV state in 14N could be due to isospin mixing. If the two levels involved are at 9.17 and 8.98 MeV, the mixing intensity is 0.41(9) with a T-mixing matrix element of 94(10) keV. Some consequences of such mixing are examined.

90.  Coexistence and B(E2)'s in 98Sr

Nucl. Phys. A 957, 184 (2017).  Published January 2017. 

I have used a simple two-state model to fit E2 strengths connecting the first two 0+  states to the first two 2+  states in 98Sr. Results for mixing parameters are in excellent agreement with those from a recent analysis. Perhaps surprisingly, they are also in remarkable agreement with results from 1980, despite the wide variation reported in the intervening years.

89.  Update on matter radii of carbon nuclei

Phys. Rev. C 94, 064307 (2016) - Published 5 December 2016

New results for matter radii of C nuclei have prompted an update on the experimental and theoretical research on this topic. Newest results for 22C suggest a major change may be needed in our understanding of the separation energy of that nucleus.

88.   (sd)4 states in 12,14Be

Phys. Rev. C 94, 064308 (2016) - Published 5 December 2016

For suggested cluster states beginning at about 10 MeV in 12Be, absolute energy and relative energy spacings agree well with calculations for the 8Be×(sd)4 configuration. Comparison indicates that the proposed (8+) state at 20.9 MeV is probably 6+. A similar calculation for 14Be predicts that the lowest (sd)2 and (sd)4 states are rather close together in that nucleus.

87.  Splitting of strengths in neutron removal from 13O

J. Phys. G: Nucl. Part. Phys. 43 115102 (2016). Published November 2016.

Using mirror symmetry and wave functions for 12Be and 13B, I have estimated the splitting of strength expected for 0 + and 2 + final states of 12O in neutron removal from 13O. Results indicate that most of the peak observed near 2.0 MeV in that reaction corresponds to a 2 + state. About 80% of the total 2 + strength should reside in a 2 + state (or states) near 5 MeV.

86.  Masses of 17,18,19,20Mg

 Phys. Rev. C 94, 044305 (2016) - Published 6 October 2016

A previous simple parametrization of mirror energy differences in pairs of nuclei consisting of a p-shell core plus two sd-shell nucleons is applied to a series of mirrors that contain sd-shell nucleons in the core. Results for 19,20Mg agree with experiment and with a potential model. Predictions are made for 2p separation energies of 17,18Mg.

85.  Solution for Energies and Mixing of Two 0+ States in 10He

Chinese Phys. Lett. 33 092101 (2016).  published September 2016.

Using results from various reactions that populate 10He, I conclude that the ground state has E 2n = 1.07(7) MeV and the excited 0 + state is in the region of 2.1–3.1 MeV. The amount of the (sd) 2 component in the ground state is less than about 0.075.

84.  Structure of 10,11Li and the reaction 11Li(p,d)10Li

Phys. Lett. B 760, 577 (2016). Published 10 September 2016.

I examine the properties of 11Li and the low-lying resonances in 10Li, as they relate to neutron removal from 11Li. Comparison with results from a recent 11Li(p,d)  reaction strongly suggests that that experiment observed only the 2+resonance, and not the 1+.

83.  Analysis of inelastic pion scattering from the low-lying 2+ states in 14C

Phys. Rev. C 94, 024345 (2016) - Published 31 August 2016

I have analyzed data for inelastic π+ and π− scatterings to the two lowest 2+ states of 14C to determine proton and neutron matrix elements. In a two-state model, I have then derived one-body transition amplitudes for p shell and (sd)2 transitions. Data are found to be consistent with equal mixing of the 2+ states but with slightly nonstandard ratios of effective charges. Using effective charges in common usage, mixing is found to be only slightly different from equal—55% of the (sd)2 component in the lower 2+ state.

82.  Single-particle s1/2 and d5/2 states in 15N and 15O

 Phys. Rev. C 94, 024339 (2016) - Published 25 August 2016

For states in 15N and 15O that have large single-particle strengths for 2s1/2 and 1d5/2, I have computed energy differences for mirror states and widths for unbound states in 15O. I consider both T=1 and T=0 cores. Calculated and experimental energies agree well. Results indicate that actual ℓ=0 spectroscopic factors for two 3/2+ states are significantly smaller than those recently reported.

81.  Coexistence and B(E2) values in 72Ge

Phys. Rev. C 94, 024318 (2016) - Published 12 August 2016

An earlier coexistence model of Ge nuclei is applied to E2 strengths connecting low-lying 0+ and 2+ states in 72Ge. New data have smaller uncertainties and, for the first time, a value for the transition strength from the third 2+ state to the second 0+ state. This B(E2) for the third 2+ state clearly indicates that it is the one that should be included in the mixing, rather than the second 2+ state. My results confirm that the 0+ states are maximally mixed, the 2+ states are weakly mixed, and the E2 matrix element involving the lower 0+ basis state is significantly larger than the one involving the second 0+ basis state.

80.  Properties of 16C(6.11 MeV) and its mirror in 16Ne

Phys. Rev. C 94, 014305 (2016) - Published 11 July 2016

From previous data for the reaction 14C(t,p)16C, I have extracted a width of 32.6(5) keV for the strong state at Ex=6.11MeV. Here, I examine its likely Jπ and configuration. The predicted width of its mirror in 16Ne is estimated to be about 260 keV.

79.  Energies and widths in 13Be

Phys. Rev. C 93, 054327 (2016) - Published 31 May 2016

I have calculated spectroscopic factors connecting three d resonances in 13Be to the three lowest states of 12Be. Combined with single-particle widths computed in a potential model, I have estimated the widths expected for the various decays. Comparing measured and calculated widths suggests that the resonance near 1 MeV is not 5/2+ and that the one just above 2 MeV is the lowest 5/2+ resonance.

78.  Structure of 16Ne(2+, Ex=6.18 MeV)

 Eur. Phys. J. A 52, 119  (2016). Published May 2016.

For several configurations that could be candidates for the structure of a recently-discovered narrow 2+ state at an excitation energy of 6.18 MeV in 16Ne, I present expected energies and widths. None is able to account for all the details of the data.

77.  B(E2) values in neutron-excess nuclei near A=16

Phys. Rev. C 93, 044322 (2016) - Published 21 April 2016

A simple model is used to compute B(E2)'s in several nuclei that have one or two sd-shell neutrons and no sd-shell protons. The model works well for all six nuclei if I use later experimental values for 16C for which the measured B(E2) is about four to eight times earlier values.

76.  Population of bound and unbound states of 12Be in proton removal from 13B

Physics Letters B 755, 351. Published 10 April 2016.

For proton removal from 13B to bound and unbound states of 12Be, I investigate the consequences of core excitation in both nuclei, using wave functions determined previously. Conclusions are that the ground state contains most of the 0+ strength, but the 2+ strength is concentrated in the second 2+ state, which is currently unknown, but predicted near 5 MeV.

75.  Widths and structure of unbound states in 12Be

Phys. Rev. C 93, 034325 (2016) - Published 21 March 2016

I have estimated the energies of several unbound states of 12Be and their spectroscopic factors for decay to the 1/2+ ground state and 1/2− first-excited state of 11Be. These are then used to estimate the expected widths for such decays. Results for likely 3− and 4+ states are good. I find that only 0+ and/or 2+ states can account for the width recently observed for a state decaying with a centroid neutron energy of 1.24 MeV.

74.  Nature of the En = 1.24 MeV state in 12Be

Eur. Phys. J. A 52, 11 (2016).  Published  January 2016

I suggest that a new state (Phys. Rev. C 90, 024309 (2014)) observed in 12Be, with a neutron decay energy of 1243 keV, is likely to be 2+, rather than the previously suggested (2−, (1−)). Primary p-wave decay is then to the first excited state of 11Be, but a possible d-wave g.s. branch could be as large as about 10%.

73.  Width of 27P(1.19MeV) and the 26Si(p,γ) reaction rate

Phys. Rev. C 92, 025807 (2015) - Published 28 August 2015

I have used a simple potential model to calculate single-particle widths in 27P. Assuming mirror symmetry, I have combined them with the spectroscopic factor from the reaction 26Mg(d,p) to compute proton widths for the 3/2+ first-excited state. I present results for the resonance strength parameter ωγ and for the (p,γ) reaction rate for two values of the γ width and two values of the resonance energy.

72.  Energies and widths of T=1 single-particle states in 14O and 14N

 Phys. Rev. C 91, 064306 (2015) - Published 11 June 2015

I used a simple potential model to compute energies and widths of single-particle states in 14O and their corresponding T=1 states in 14N, using information for the parent states in 14C as input. Agreement is reasonable, but some discrepancies exist.

71.  Lowest (sd)2 states in odd-A light nuclei

Phys. Rev. C 91, 044321 (2015) - Published 22 April 2015

A simple two-component shell-model calculation has previously been successful in predicting the absolute energies of 0+(sd)2 states in several light nuclei. Here, I apply the same model to such states coupled to odd-A p-shell cores.

70.  Properties of 15Be(5/2+)

Phys. Rev. C 91, 034314 (2015) - Published 11 March 2015

A simple (sd)3 shell-model calculation has previously worked extremely well in predicting absolute energies of the lowest 5/2+ state in 19O,17C, and 13Be. Here, I apply the same model to 15Be. When combined with a recent experimental result, the analysis produces tight constraints on the s and d single-particle energies in 13Be.

69.  Constraints on energies of 10He(0+) and 9He(1/2+)

 Phys. Rev. C 91, 034306 (2015) - Published 3 March 2015

I have used the relationship between computed energies in 10He and single-particle energies in 9He to provide limits on the s1/2 energy. The absence of any bound states in 10He requires Es>1MeV, contradicting all the experiments that have reported an s state near threshold. The present analysis supports the view that the variation of 10He “ground-state” (g.s.) energies determined in various reactions is caused by the presence of two overlapping 0+ resonances. Results of the two simplest reactions—proton knockout and (t,p)—have been used to extract the g.s. and excited 0+ energies as a function of the mixing parameter b2 between the p-shell and the (sd)2 basis states.

68.  Structure of 11Li(g.s.) and an excited 3/2− state

Phys. Rev. C 91, 017303 (2015) - Published 12 January 2015

New measurements of reaction cross sections for scattering of 11Li from H and C have provided a value for the radius of the neutron density distribution. By using the sensitivity of calculated radii to neutron configuration, I find that the s2 fraction required to reproduce the new radius is P(s2)=0.33+0.03−0.05, in agreement with an earlier estimate of 0.33(6). Calculations of relative cross sections for the reaction 9Li(t,p) (in reverse kinematics) suggest a method to observe an expected excited 3/2− state and to independently determine P(s2).

67.  14Be(g.s.) and single-particle energies in 13Be

Phys. Rev. C 90, 064305 (2014) - Published 1 December 2014

Coupling two sd-shell neutrons to a pure p-shell 12Be ground state (g.s.), rather than to the physical g.s., removes difficulties in applying a previous simple model to 14Be. I have calculated the g.s. wave function in this simple model, and have estimated the 2s1/2 single-particle energy.

66.  Reexamining shell-model predictions for the mass of 17Na(g.s.)

Phys. Rev. C 90, 067302 (2014) - Published 1 December 2014

A new shell-model calculation for 17C provides spectroscopic factors for use in a computation of mirror energy differences between 17C and 17Na. Results are compared with previous predictions.