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Neutron angular distributions from the ($p, n$) reactions in ${\mathrm{C}}^{13}$, ${\mathrm{B}}^{11}$, and ${\mathrm{Be}}^{9}$ have been measured using a long-counter detection technique in conjunction with the Livermore 90-inch variable-energy cyclotron. Proton energies ranged from threshold (2.0 Mev to 3.2 Mev) up to 5.7 Mev. The aim here was to find qualitative experimental evidence bearing on the direct reaction mechanism proposed by Bloom, Glendenning, and Moszkowski wherein the ($p, n$) reaction connecting the ground states of mirror nuclei should go via a direct mode which is derived principally from the residual two-body interaction between the incoming proton and the bound neutron (or neutrons). It is found that the experimental evidence supports this hypothesis in that the angular distribution changes slowly in the direction of increasing complexity with increasing energy, largely ignoring the occurrence of resonances except in their immediate vicinity. Also a tentative grouping by pairs of the ($p, n$) angular distributions for (${\mathrm{C}}^{13}$, ${\mathrm{N}}^{15}$) and (${\mathrm{Be}}^{9}$, ${\mathrm{B}}^{11}$) shows marked similarities between the members of each pair in conformity with the twin-reaction picture stemming from the same theory. Finally, preliminary results are presented of an IBM-704 computation program using a distorted-wave Born approximation theory formulated originally by Glendenning. The comparison between theory and experiment, although based on early returns, is in general encouraging. It is found that a triplet-singlet interaction strength ratio is required here which is about $\frac{2}{3}$ of that derived from the Gammel-Thaler phenomenological potential. However, in view of the basic differences between the free and the bound two-body problem it is felt that more knowledge will be required in order to properly compare the present results with the free-scattering analyses.

Angular correlation studies with the 24 Mg ( p ,α) 21 Na (P O ) 20 Ne reaction establish J = 5 2 and 1 2 spin assignments for the respective 3540 and 2804 keV 21Na states. Mirror pair identification between the 21Ne 2790 keV and 21Na 2804 keV states indicates a J π = 1 2 − assignment thereto.

Allowed beta transitions of the G-T type, p 3 2 → p 1 2 in the Ga-Sr region, g 9 2 → g 7 2 in the Rh-In region and d 5 2 → d 3 2 in the Sb-Nd region are investigated in terms of pairing theory. It is found that experimental ƒt values can be explained as the effect of pairing correlation. Fractional occupation parameters U and V are derived from the experimental data, by using simple theoretical formulae. The values thus obtained are found to be quite consistent with those obtained from the cross-sections of (d,p) and (d,t) reaction studies. The U and V values determined by this treatment are compared with those calculated by using the newly adopted nuclear parameters of pairing theory. The B value defined as ƒt = Bξ/|>j f ||σ||j 1 2 is deduced. The mean log B value is found to be 4.46, 4.86 and 5.00 for the first, the second and the third region, respectively. The B value is 9 to 30 times larger than that in transitions between mirror nuclei. The results may imply that the alowed beta transitions are more hindered in a nuclear region with heavier mass number.

A magnetic-lens type beta-ray spectrometer has been used to measure the relative intensities of internal conversion electrons and also of photoelectrically converted gamma-rays for ground state transitions of the first- and second-excited levels of Ne19. These levels of Ne19 were excited by the reaction F19(p, n)Ne19∗. The relative intensities of the internal conversion electrons and the photoelectrons show that the internal conversion coefficient for the first-excited to ground state transition is about an order of magnitude larger than the internal conversion coefficient for the second-excited to ground state transition. Therefore, the first-excited level of Ne19 must have a larger total angular momentum than the second-excited level. This result confirms the interpretation given to the mean life measurements of these transitions; consequently, the reversed spin sequence of the first- and second-excited levels in the mirror nuclei Ne19 and F19 appears now to be well established. The level energies inferred from the photoelectron and internal conversion electron spectra are 241±4 and 271±4 keV for the first- and second-excited levels of Ne19.

Recent measurements of the electron asymmetry of Σ−n beta-decay and that of eν correlation and asymmetries of Λp decay are analysed including pseudotensor andq2-dependent form factors. The result is compared with Wilkinson’s measurement of pseudotensor contributions in beta-decay of mirror nuclei, assuming someSU3 structure of a second-class current. Possible consequences of octet and decuplet representations of the second-class axial vector current are discussed.

The ($^{3}\mathrm{He},t$) and ($^{3}\mathrm{He}$,$^{3}\mathrm{He}$\ensuremath{'}) reactions on $^{9}\mathrm{Be}$, $^{12}\mathrm{C}$, $^{13}\mathrm{C}$, $^{14}\mathrm{C}$ [($^{3}\mathrm{He},t$) reaction only], $^{14}\mathrm{N}$, and $^{15}\mathrm{N}$ have been investigated at $^{3}\mathrm{He}$ energies varying between 40 and 50 MeV. Angular distributions were obtained for all prominent states up to excitations of 20 MeV. A microscopic analysis of these data has been carried out, using a local two-body interaction with an arbitrary spin-isospin exchange mixture. Spectroscopic factors were calculated, using intermediate-coupling wave functions for $p$-shell states, while simple $j\ensuremath{-}j$ configurations were assumed for the levels which were populated by promoting a $p$ nucleon to the $s\ensuremath{-}d$ shell. A Yukawa interaction with a range of 1.2 F was found to give the best results. The strength of the effective nucleon-nucleon interaction required to fit these data is in good agreement with recent analyses of the ($p,{p}^{\ensuremath{'}}$) and ($p,n$) reactions on light nuclei. In particular, dominant $L=0$ transitions observed in the ($^{3}\mathrm{He},t$) reaction give values for the isospin-dependent (${V}_{\mathrm{ST}}={V}_{01}$) and spin-isospin-dependent (${V}_{11}$) terms (converted to an effective nucleon-nucleon interaction at a range of 1.0 F) of 20.6 and 16.5 MeV, respectively, while the strengths required to fit ($^{3}\mathrm{He},t$) $L=2,3$ transitions were generally enhanced. For inelastic transitions, the average strengths obtained for ${V}_{00}$, assuming a Serber exchange mixture, varied from 47.2 to 67.3 MeV, depending upon the $L$ transfer involved. A comparison of the ($^{3}\mathrm{He},t$) and ($^{3}\mathrm{He}$,$^{3}\mathrm{He}$\ensuremath{'}) reactions populating analog final states (where ${T}_{f}={T}_{i}+1$) is also presented. In general, these transitions were weak; however, it was possible to observe the lowest $T=\frac{3}{2}$ levels in the mirror nuclei $^{9}\mathrm{B}$-$^{9}\mathrm{Be}$ and $^{13}\mathrm{N}$-$^{13}\mathrm{C}$, and several $T=1$ levels in $^{12}\mathrm{N}$-$^{12}\mathrm{C}$.

Measurements of the capture $\ensuremath{\gamma}$-radiation processes, $\mathrm{mass} 3+\ensuremath{\alpha}\ensuremath{\rightarrow}\mathrm{mass} 7+\ensuremath{\gamma}$ and $\mathrm{nucleon}+{\mathrm{Li}}^{6}\ensuremath{\rightarrow}\mathrm{mass} 7+\ensuremath{\gamma}$, give information about the cluster structure of the mirror nuclei ${\mathrm{Li}}^{7}$ and ${\mathrm{Be}}^{7}$. The cluster model predicts that the ground state and low excited states of these nuclei should have large reduced widths ${{\ensuremath{\theta}}_{3+4}}^{2}$ for the configuration $\mathrm{mass} 3+\ensuremath{\alpha}$ particle and small reduced widths ${{\ensuremath{\theta}}_{1+6}}^{2}$ for the configuration nucleon +${\mathrm{Li}}^{6}$. Scattering experiments provide accurate initial, capturing, wave functions, and an assumption of the cluster nature of the final, bound, states allows the electromagnetic capture cross sections to be calculated and compared to experiment. The reduced widths deduced show that ${{\ensuremath{\theta}}_{3+4}}^{2}$ is large, ${{\ensuremath{\theta}}_{1+6}}^{2}$ is small, and that the ground states and first excited states of ${\mathrm{Li}}^{7}$ and ${\mathrm{Be}}^{7}$ are primarily of the two-body cluster form $\mathrm{mass} 3+\ensuremath{\alpha}$ particle.

Investigation of the electromagnetic transitions in 25 Mg has led to the determination of the following parameters: the branching ratios of the third to eighth excited states inclusive; the multipole mixing ratios of the 1.960 → 0, 1.960 → 0.975 and 3.400 → 1.614 MeV transitions; the spins and parities of the 1.614, 2.738 and 3.400 MeV levels and the lifetime of the 3.400 MeV level. The experimental results are compared with the corresponding results in the mirror nucleus 25 Al, and experimental information is presented relating to the rules governing the strength of corresponding transitions in mirror nuclei. The experimental results are also compared with the predictions of the strong-coupling rotational model.

The branching ratio of the electromagnetic decay of the J π = 1 2 + level at 2.393 MeV in 23 Na has been determined from a study of the 22 Ne( 3 He, dγ) 23 Na reaction using particle-gamma coincidence technique. Theoretical calculations using the collective model and including isospin as a good quantum number seem to account for the experimental result as well as the vastly different branching ratio for the corresponding level in 23 Mg.

A new level in 25 Al at E x = 6328 ± 3 keV has been located as a resonance in the 24 Mg(p, p′γ) reaction at E p = 4227 ± 2 keV. From proton and γ-ray angular distributions J = 7 2 is assigned to the resonance. Very low limits ( θ l 2 ≈ 10 −4 ) on the proton reduced widths are imposed by the intensities of the resonant elastic and inelastic scattering. The reduced widths are similar to those of the known E p = 2.007 MeV , J π = 3 2 + and the E p = 2.408 MeV , J π = 5 2 6+ resonances. The three levels are suggested to be the lowest members of a K π = 3 2 + band. The corresponding J π = 3 2 + , 5 2 + levels in the mirror nucleus 25 Mg have been investigated with the 23 Na( 3 He, p) reaction. A L = 0 two-particle transfer was observed to the J π = 3 2 + level. The relevance of this result is discussed.

It is found that core-deformations, as treated by Nilsson, can account for a major part of the many types of discrepancy between simple shell-model expectations and observed trends in beta-decays rates, among very light as well as heavier nuclei. Not only are the well-known suppressions of normal allowed transitions relative to shell-model expectations treated, but similar suppressions among forbidden transitions, distinguished here for the first time. Significant confirmation for applications of the deformed-core picture even to mirror nuclei comes from a correlation discovered between certain l -forbidden decay enhancements and super-allowed decay suppressions.

The recent measurements of the lifetimes of the first excited states of the mirror nuclei O/sup 17/ and F/sup 17/ raised new interest in the various theoretical interpretations of these lifetimes. The weak-coupling collective model of Bohr and Mottelson was applied to these E2 transitions and to the similar E2 transitions that were measured in N/sup 16/ F/sup 19/ and Ne/sup 19/. If harmonic oscillator radial wave-functions were used in evaluating the radial integrals in the theory, the predictions matched the experimental results for the E2 transition probabilities in N/sup 16/, O/sup 17/, F/sup 17/, and F/sup 19/ >s and the quadrupole moment of O/sup 17/. The theoretical prediction was an order of magnitude smaller than the experimental result for transition probability of the first excited state of Ne/sup 19/. (auth)

The theory of pion quasi-elastic scattering leading to nucleon emission from nuclei at pion energies near the (3, 3) resonance energy is investigated. The importance of final state interactions between the outgoing nucleon and the residual nucleus is studied with particular emphasis on the relative cross sections for the reactions A ( π + , πN ) and A ( π − , πN ) and also for the reactions A ( π − , π − n ) and A ( π − , π − p ) which produce mirror nuclei in the final state. A reasonably consistent description of the available data is obtained only if compound nucleus effects are included in the final state interaction. Using an isospin basis the remarkable deviations from the simple plane wave impulse approximation theory observed in several experiments are seen to arise from the complete coherence assumptions inherent in the plane wave approach. Predictions from the present approach are made for target nuclei with nonzero neutron excess for both (π, πN ) and (π, π′) processes.

A correction to the Coulomb displacement energies arising from the isovector monopole state is calculated using a sum rule approach.

In mirror nuclei with one valence nucleon outside a doubly closed-shell core, there has been a long-standing discrepancy between experimental and theoretical values of their mass-splitting. If the matter distribution of the core protons in the neutron-rich storage is slightly larger in radius than that for the core protons in the proton-rich analogue, this discrepancy can be explained.

We have measured branching ratios for the isospin-nonconserving particle decays of the 15.1-MeV $T=\frac{3}{2}$ states in $^{13}\mathrm{N}$ and $^{13}\mathrm{C}$ to the (0.0, ${0}^{+}$) and (4.44, ${2}^{+}$) states of $^{12}\mathrm{C}$. By comparing ratios of reduced widths with the ${0}^{+}$ and ${2}^{+}$ states of $^{12}\mathrm{C}$ for the mirror decays, we show that the form of the isospin impurity in the 15.1-MeV states depends on ${T}_{z}$.

The experimental arrangement and method of investigation by the photographic plate technique of (d, n) reaction at a deuteron bombarding energy of 8 MeV are described. The positions are reported of some of the energy levels of the residual nuclei 13N, 17F and 33Cl. It has also been possible to determine spins and parities of the corresponding levels from measurements of the angular distributions of some of the neutron groups. A comparison of the mirror nuclei 13C13N, 17O17F and 33S33Cl is made.

A summary of the knowledge of the low-energy interaction of two nucleons with one unit of isobaric spin is presented. The single energy analyses of accurate low-energy proton-proton scattering data are discussed with emphasis upon the electromagnetic effects which have been included and those which should be. The phase shifts which result are presented and discussed in terms of the effective range expansion and potentials. A brief discussion of charge symmetry and independence in terms of potentials and dispersion relations is given. The equality of the neutron-neutron and proton-proton nuclear interactions, which seems to be established, may not be sufficient for understanding the problem of mirror nuclei. The question of charge independence is much more difficult.

The differences in energies of the corresponding levels in mirror nuclei of the 1p shell are calculated. Coulomb forces, neutron-proton mass difference and the electromagnetic spin-orbit forces are included in the calculation. Intermediate coupling is used and the integrals involved are evaluated consistently for a physically reasonable value of the nuclear radius. No evidence is found for any breakdown of charge symmetry.

A detailed study of the variations of the difference between the proton-nuclear potential and the neutron-nuclear potential is carried out using ground-state mass data. A previous analysis of mirror nuclei has delimited the problem and suggested that the well difference can be neither constant nor strictly $Z$ dependent. It is found by using analytical techniques as well as calculations performed with the Oak Ridge Oracle that the potential anomaly varies with the symmetry parameter $\frac{(N\ensuremath{-}Z)}{A}$ and that the proportionality constant does not change very greatly as one proceeds from a static well to a velocity-dependent well. This is somewhat surprising in view of many studies which suggest that the nuclear symmetry energy is considerably influenced by the velocity dependence of the nuclear potential. The relative insensitivity to velocity dependence or nonlocality is attributed to surface effects not taken into account in the analyses of infinite nuclear matter.A number of possible origins of the well differences are examined including (a) the failure of Koopman's theorem, (b) the breakdown of electrostatic laws, (c) the presence of Heisenberg forces, (d) the effect of the exclusion principle, and (e) the spin dependence of nuclear forces. It is concluded that the last two effects account for the bulk of the proton potential anomaly. Indeed, these last two effects suggest that the well depths used in neutron scattering and in proton scattering vary individually with the symmetry parameter, and it is suggested that experimentalists attempt to seek out these variations in careful, low-energy scattering experiments.

An analysis employing the recent nuclear reaction theories of Wigner and others is given of the experimental data on the low energy interactions of $s$, $p$, $d$ orbital neutrons and protons with ${\mathrm{C}}^{12}$ and $s$ neutrons and protons with ${\mathrm{O}}^{16}$. Assuming the equality of $\mathrm{nn}$ and $\mathrm{pp}$ nuclear interactions, it is possible to account for the data on the $s$ interactions if the level spacing is considered in addition to the customary two resonance parameters: reduced width and level position; in particular, the displacement of conjugate levels can be attributed to the difference of the external wave functions for the odd particle, although with an uncertainty of about 25 percent which is due primarily to the lack of precise knowledge of the internal Coulomb energy of the excited states. The large magnitudes of the reduced width and level spacing indicate that two-body potential interactions exist between the odd particle and the ${\mathrm{C}}^{12}$ and ${\mathrm{O}}^{16}$ cores, and the values of the respective logarithmic derivatives indicate that these interactions are of about equal strengths. The energy dependence of the radiative capture cross section of $s$ neutrons and protons with ${\mathrm{C}}^{12}$ can be understood if an additional quantity, the final-state reduced width, is included in the theory to take into account the energy-dependent external contribution to the transition moment. The experimental data are only sufficient to treat the $p$ and $d$ interactions in the one-level approximation; a reasonable explanation can be given of the observed displacements of conjugate levels in terms of the differences of the electromagnetic properties of the odd particle such as: external wave functions, spin-orbit interactions, and variations of the internal Coulomb energy. There is some indication from the data on radiative transitions that the independent-particle model also prevails in the $p$ states; on the other hand, the small reduced widths of these states suggest a many-body description. Derivations based on the recent theories are given of the one-channel formulas and of the general one-level formulas which include the negative-energy alternatives. The radial dependences of the resonance parameters are discussed.

Synopsis Measurements are described of the angular distributions of the four most energetic neutron groups from the 10 B( d, n ) 11 C reaction at a deuteron energy of 0.6 MeV. Neutrons were detected by their recoil protons in nuclear emulsions. The angular distributions have been analyzed in terms of a stripping contribution and an, assumedly isotropic, contribution from compound nucleus formation. From Butler analysis l p = 1 is found for the stripping contribution of the neutron group leading to the 11 C ground state, and l p = 0 for the group leading to the second excited state. This is in agreement with previous results obtained from the mirror reaction 10 B( d, p ) 11 B and with predictions from the nuclear shell model. Stripping contributions of the other two neutron groups are very small.

The empirical Coulomb-energy differences of single-particle states are plotted for T z = ± 1 2 mirror nuclei having mass numbers A = 4n+ 1. At A = 29, they decrease systematically in theorder 1 d 3 2 , 2s 1 2 , 1 7 2 , 2p 3 2 and 2p 1 2 . With appropriate omissions, the same sequence is observed at the higher mass numbers A = 33, 37 and 41. Except for the inversion of the 2s 1 2 and 1d 3 2 states at A = 29, the pattern is very similar to the one in the neutron separation energies Sn of the same states. The latter represent the nuclear interaction of the odd nucleon with the core, which is compared with the Coulomb interaction of the odd proton with the core. At least for A = 13 and 17, the 2s 1 2 . states have a relatively low Coulomb-energy difference. Another exception occurs for the 1d 3 2 and 1f 7 2 single-particle levels at A = 17, which have a relatively large Coulomb-energy difference that is close to the one of the 1d 5 2 ground state.

It is shown that charge independence or charge symmetry give rise to the following relations connecting the strengths of gamma -transitions between corresponding states in mirror nuclei: (a) the strengths of corresponding El transitions are always equal; (b) the strengths of corresponding M1 transitions should not differ in general by more than a factor 1.5; (c) for transitions with STA DELTA T! = 1 the strengths of corresponding transitions of any multipolarity are equal. The effects of the Coulomb and exchange corrections to the above rules are examined. The experimental data presently available are discussed. (auth)

A semiclassical expression for Coulomb energies of the mirror nuclei has beeb derived. The exchange part in the above expression is derived on a statistical model which gives in addition to the usual term, a pairing effect of magnitude 0.33. Inconsistencies in some of the earlier expressions have been pointed out. The radius parameter r0 from this formula agrees very well with the electron scattering values. A more detailed calculation of the Coulomb energies in LS-coupling shell model with constant values of the parameters within a shell gives least squares fit with an r.m.s. deviations of nearly 4 % in both p and d-shells. The least squares fit parameters are not satisfactorily reproduced by the harmonic oscillator wave function. The variation of the h.o. strength parameter α = ωM/ℏ within p and d-s shell has been studies. A comparison of the r.m.s. radius from Coulomb energies and electron scattering shows a discrepancy of about 8 % in case of Be9. The vanishing of the second difference of Coulomb energy and its negative value at a shell crossing are found to agree with the detailed shell model calculation.

Experimental values of energies of mirror nuclei are analysed. The results permit to improve the theory of beta-decay.

The Carlson-Talmi shell-model theory for Coulomb energies of mirror nuclei indicates an appreciable discontinuity of the harmonic oscillator parameter e 2 (v/π) 1 2 and the nuclear radius parameter r0 at A = 29. To be more realistic, configuration mixing within the sd shell at least should be taken into account. Considerations of a qualitative nature suffice to show that thereby the discontinuity loses its significance.

The 3.68 mev 3/2 - state of 13C is shown, by a coincidence technique to cascade via the 3.09 mev 1/2+ state with a probability of (6−5±1.0) × 10−3. The rule that Corresponding E1 transitions in mirror nuclei have the same reduced speed, i.e. are mirror transitions, is used to deduce the speed of this weak branch from data available in 13N and hence to determine the radiative width of the M1 transition to ground from the 3.68 mev state. This is (0.40–0.75) ev. The speed of this transition, which is not a mirror transition to the corresponding one in 13N, is compared with the prediction of the independent particle model. Agreement is obtained within the range of the intermediate coupling parameter a/K that satisfies other data in the A =13 system.

It is noted that the deviations of the isoscalar magnetic moments from Schmidt values behave in a systematic way, being positive for the jackknife cases and negative for the stretch cases. Other subjects of interest concerning magnetic moments are discussed.NUCLEAR STRUCTURE Systematics of isoscalar magnetic moments.

Very simple relations between renormalization factors and corrections to the GT-typeΒ-decay operator, isovector magnetic moment and coulomb energy differences between mirror nuclei due to tensor correlations are obtained.

Examination of the ground-state transitions of the (p,t) and (p,/sup 3/He) reactions on all T/sub z/=1/2 nuclei from /sup 21/Ne through /sup 39/K reveals a systematic suppression of the S=1, T=0 component of the (p,/sup 3/He) transfer cross sections which is not explained in terms of current structure and reaction theories. (AIP)

At 5/sup 0/ and 292 MeV, the A dependence of pion-induced double-charge-exchange cross sections on T = 1 targets differs significantly from the A/sup -10/3/ behavior expected theoretically. The addition of a second process, whose cross section varies as A/sup -4/3/, provides a good fit to the data. The resulting two-amplitude model predicts cross sections for heavier (T>1) nuclei that are in agreement with experiment.

Sugimoto, Tanihata and Goring's experimental data on the energy dependence of the asymmetries of beta-rays emitted from polarized 12B and 12N nuclei are analyzed in an almost nuclear model independent way. The analysis suggests the existence of second-class currents. New limits on KDR's second-class current parameters ζ and λ are estimated.

Most nuclei have a nearly spherical shape and can be characterized by an effective radius R=R0 A1/3, where A is the nucleon number and R0 is a constant to be determined from experimental data. Traditionally, the data came from experiments on muonic or pionic x‐ray emission, high‐energy electron scattering, optical or x‐ray isotope shifts, β emission by mirror nuclei, α decay, or neutron scattering. Because this type of information is not readily available in textbooks or the pedagogical literature, it is difficult to ask students to establish the radius formula on their own. However, as shown here, one may easily circumvent the difficulty by using the readily available and highly accurate masses of the mirror nuclei. Results are presented for all existing pairs of mirror nuclei.

The β+ decay of 45V (J π , T= 7 2 − , 1 2 ) has been observed. The half-life was found to be 539 ± 18 ms; in addition to the superallowed transition to the mirror state (45Ti ground state), it exhibits a (4.3 ± 1.5)% allowed branch to the 5 2 − state at 40.1 keV in 45Ti. Decay data for the complete f 7 2 shell series of mirror nuclei are presented.

The iso-vector magnetic moments of mirror nuclei in the 1p-shell and the beta decays between them are studied. A clear evidence is shown in order to indicate that mesonic effects on the iso-vector magnetic moments differ from those on the beta decays.

A total width ${\ensuremath{\Gamma}}_{\mathrm{c}.\mathrm{m}.=303\ifmmode\pm\else\textpm\fi{}30}$ eV was found for the ${J}^{\ensuremath{\pi}}$, T${=(1/2)}^{\mathrm{\ensuremath{-}}}$,(3/2) level at 16.98 MeV in $^{9}\mathrm{Be}$ by employing high resolution beams of our 450 kV electrostatic accelerator. Partial widths of selected decay channels are given. A comparison with existing data of the lowest T=(3/2) level in the same nucleus as well as the ones in the mirror nucleus $^{9}\mathrm{B}$ is made. The results are discussed in terms of isospin mixing.

A heavy-ion reaction leading to two members of the same isospin multiplet in the exit channel has been studied. The angular distribution is symmetric about 90°. This proves the “indentity” of mass 13 mirror nuclei, as seen from a nuclear reaction in which isospin is concerned.

Distributions of electrons elastically scattered by He/sup 3/ and T are compared in order to analyze the three-body forces acting in these mirror nuclei. The charge and magnetic form factors for the nuclei are calculated. Three of these form factors are nearly equal to one another but the charge form factor of He/sup 3/ is different from the other three. (T.F.H.)

Nuclear matter raddi were calculated from measured Coulomb energy differences and charge radii. The Coulomb energy differences were taken between nuclear states that are members of an isobaric-spin multiplet. A significant anomaly in the radius of the excess nucleons was found. In the mirror pair 41 Ca- 41 Sc, for instance, the known charge radius of the 40 Ca core was used to extract the rms radius for the 41st nucleon. This radius is virtually the same as that of the 40 Ca core, whereas any simple potential model would predict the 1f 7 2 orbit to be ∼ 20% larger than the average radius of the lower orbits. This qualitative effect is present in other mirror nuclei, and is also a feature of Coulomb energy differences from isobaric-spin analog states in heavier nuclei, for which the neutron excess is larger.

Analog (fp)3 states preferentially excited in the 40 Ca ( 6 Li,t ) 43 Ti and the 40 Ca ( 6 Li , τ) 43 Sc reactions have been identified in the mass 43 mirror nuclei. A simple zero-range DWBA calculation made with a cluster form factor gives good agreement with the measured angular distributions, but spectroscopic strengths deduced for mirror levels do not agree. The 3p-0h states are excited with a rather uniform cross section not strongly correlated with spins.

The g -factor of the τ 1 2 =22 μ s , J π =(7 + ), T=0 isomeric state at 3.46 MeV in 38 K has been measured by the differential spin precession method with the 35 Cl (α, n ) 38 K reaction. The result of g =+0.548 ( μ =+3.836± 0.014 n.m.) is consistent with a pure f 7 2 2 , J π =7 + configuration.