The 10 even-odd nuclei with an odd number of nucleons, $\xi =11\mathrm{}$:${}_{}{}^{19}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{21}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{23}{}_{}{}^{}\mathrm{Mg}$; and $\xi =13\mathrm{}$:${}_{}{}^{23}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{25}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Si}$ have been studied in the framework of the Bohr-Mottelson and Nilsson models. Two different methods of calculation have been used for the energies and wave functions of positive- and negative-parity states. The ground-state static moments and $M1\mathrm{}-E2\mathrm{}$ transition rates have been computed. A minimum number of phenomenological parameters have been used. It has been confirmed that these nuclei (except ${}_{}{}^{19}{}_{}{}^{}\mathrm{O}$) show an equilibrium prolate deformation and can be well accounted for by the model, especially as concerns the positive-parity particle states. Difficulties arise for most of the hole states and negative-parity particle states. Parameters are found to be in the same range for all nuclei. General conclusions on the validity of the model have been discussed in the lower part of the $2s-1d$ shell.

An improved method of calculating the form factor for the distorted-wave Born-approximation treatment of ($p,\alpha$) reactions is described that incorporates explicitly the nuclear structure information. The improvement over earlier treatment of the ($p,\alpha$) reaction is achieved by carrying out a transformation to center-of-mass and internal coordinates of the transferred nucleons, whose individual wave functions are calculated in a Woods-Saxon potential. The formalism is applied to an analysis of the ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}(p,\alpha ){}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ reaction performed at a proton bombarding energy of 40.2 MeV. Relative proton spectroscopic factors are deduced for the relatively pure single-hole states at 0.0 (${\frac{3}{2}}^{+}$) and 2.52 (${\frac{1}{2}}^{+}$) MeV in ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}$. Good agreement with the proton spectroscopic factors from the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(d,{}_{}{}^3{}_{}{}^{}\mathrm{He}){}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ reaction is achieved. The ${\frac{5}{2}}^{+}$ states in ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ whose structure is largely unknown contain components important to the ($p,\alpha$) reaction, but not to the ($d$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$) reaction, as evidenced by their relatively stronger excitation in the ($p,\alpha$) reaction.

Neutron spectra from the ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}\mathrm{}(p,n)\mathrm{}{}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$ reaction have been measured at bombarding energies of 18, 20, 22, 24, and 26 MeV. The portion of the spectra corresponding to residual excitations of 10 MeV or less was compared to a shape calculated under the assumption that the residual levels are two exciton proton-particle neutron-hole states. Good agreement was obtained at 22, 24, and 26 MeV, but the spectra at lower bombarding energy could only be fitted with the addition of contributions from four exciton states. The inclusion of pairing effects improved the agreement between the calculation and the data. The data were also compared to a calculation with the hybrid model for preequilibrium reactions; good agreement was observed.

[NUCLEAR REACTIONS ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}\mathrm{}(p,n)\mathrm{}{}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$, $E_p=18,20,22,24,26\mathrm{}$ MeV; measured $\sigma ({\mathrm{E}}_n,\theta )$, $\theta =24-{144}^{\circ }$.]

The lifetimes of the first two excited states in ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$ have been investigated using the reaction ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}({}_{}{}^3{}_{}{}^{}\mathrm{He},n\gamma ){}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$ and the Doppler-shift attenuation method. Pulse-shape discrimination was employed for the neutron-$\gamma$-ray coincidence measurements. These measurements lead to the following mean lives: $\tau \left(2699\mathrm{} \mathrm{keV}\right)={76}_{-24\mathrm{}}^{+49\mathrm{}}$ fsec and $\tau \left(3924\mathrm{} \mathrm{keV}\right)>\mathrm{}1\mathrm{}$ psec. The $E2\mathrm{}$ transition strength for the $2^{+}\to 0^{+}$ transition is compared to shell-model predictions.

Measurements of the ${}_{}{}^{43}{}_{}{}^{}\mathrm{Ca}\mathrm{}(d,t)\mathrm{}$ and ${}_{}{}^{41}{}_{}{}^{}\mathrm{K}({}_{}{}^3{}_{}{}^{}\mathrm{He},d)$ reactions have been carried out at incident energies of 20 and 23 MeV, respectively, with an energy resolution of 9-14 keV full width at half maximum. Single-particle strength distributions have been studied up to an excitation energy of 6.24 MeV in ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$. About 75% of the total $l=3\mathrm{}$ pickup strength is observed in the even-parity states up to the $6^{+}$ state at 3.188 MeV. The other 25% is distributed over 10 states between 3.2 and 6.2 MeV. The $l=2\mathrm{}$ pickup transitions should populate four $T=1\mathrm{}$ states of the [${\left(1\mathrm{}{f}_{\frac{7}{2}}\right)}^3\times {1d_{\frac{3}{2}}}^{-1\mathrm{}}$] multiplet with $J^{\pi }={\mathrm{}(2,3,4,5)\mathrm{}}^{-}$. The strength is found to be spread over at least 20 states, however, and many transitions show considerable $l=0\mathrm{}$ admixture. The stripping measurements also show extensive fragmentation of the $l=3\mathrm{}$ strength leading to the negative-parity states of ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$, and large differences are observed between the strength distributions observed in stripping and pickup to these states. The particle transfer measurements were supplemented by high-resolution measurements of the ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}(\alpha ,{\alpha }^{\prime })$ reaction at 28.5 MeV which provided definite spin-parity assignments to many natural parity states in ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$.

Measurements of the ${}_{}{}^{49}{}_{}{}^{}\mathrm{Ti}\mathrm{}(d,t)\mathrm{} {}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$ reaction have been carried out at 18 MeV with an energy resolution of about 10 keV. Single-particle strength distributions for $l=0,2,\mathrm{and} 3$ have been obtained up to excitation energy of 7 MeV in ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$. About 85% of the $l=3\mathrm{}$ strength is found in states below 3.6 MeV, and the total $l=3\mathrm{}$ strength is consistent with the sum rule limit for $1f_{\frac{7}{2}}$ transfer to $T=2\mathrm{}$ states. About three quarters of the sum rule limit for the $l=2\mathrm{}$ strength (assumed be $1d_{\frac{3}{2}}$) and half the limit for the $l=0,2\mathrm{}{s}_{\frac{1}{2}}$ strength is observed, with lower limits for the centroid energies of 5.36 and 5.17 MeV for the $1d_{\frac{3}{2}}$ and $2s_{\frac{1}{2}}$ hole, respectively. Measurements of inelastic $\alpha$ scattering on ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$ have also been carried out at an incident energy of 28.5 MeV with a resolution of 18 keV. These measurements provide many new spin-parity assignments for natural parity states in ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$. In combination with the pickup measurements, they provide identification for the centroids of the $J^{\pi }={\mathrm{}(2,3,4,5)\mathrm{}}^{-}$ states of the (${f_{\frac{7}{2}}}^9\times {d_{\frac{3}{2}}}^{-1\mathrm{}}$) multiplet.

Accurate excitation energies were measured for 42 states in ${}_{}{}^{25}{}_{}{}^{}\mathrm{Al}$. The ones below 3.7 MeV were measured with both the ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}({}_{}{}^3{}_{}{}^{}\mathrm{He},d){}_{}{}^{25}{}_{}{}^{}\mathrm{Al}$ and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}(\alpha ,p){}_{}{}^{25}{}_{}{}^{}\mathrm{Al}$ reactions to an accuracy of 2.5 keV or better. Excitation energies between 3.7 and 7.9 MeV were measured with the first reaction only. Uncertainties for the narrow states range from 2.5 to 7 keV with two exceptions. Nine states were found to have natural widths greater than 15 keV and these were measured. The agreement with previous work is excellent in the region below 3.7 MeV and is especially good with four excitation energies deduced from $\gamma$-ray energy measurements. Nine new states were found between 3.7 and 7.9 MeV and above 5 MeV our accuracy is much better than that previously reported for all but the known state at 6.3 MeV. We find ground-state $Q$ values of -7709.3 ± 2.6 keV for the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}(p,\alpha ){}_{}{}^{25}{}_{}{}^{}\mathrm{Al}$ reaction and -3218.0 ± 4.5 keV for the ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}({}_{}{}^3{}_{}{}^{}\mathrm{He},d){}_{}{}^{25}{}_{}{}^{}\mathrm{Al}$ reaction. These results agree within 0.3 keV as to the mass of ${}_{}{}^{25}{}_{}{}^{}\mathrm{Al}$ but the value is 5.3 keV lower than that in the latest mass compilation.

The results of neutron resonance time-of-flight spectroscopy measurements using the Nevis synchrocyclotron are given for the separated W isotopes (182, 184, 186) and for natural W. Almost all $s$ levels were observed to 2.65 keV, and resonance $\mathrm{}\left(g\right)\mathrm{}{\Gamma }_n^o$ values presented to ∼16 keV for the above even isotopes, and to 700 eV and 2.6 keV, respectively, for ${}_{}{}^{183}{}_{}{}^{}\mathrm{W}$. The ${}_{}{}^{183}{}_{}{}^{}\mathrm{W}$ level assignments were from levels in natural W which were not assigned to the other isotopes. A Bayes's theorem analysis shows that nearly all of the observed levels are $s$ rather than $p$ levels, since W is at a maximum for the $s$ strength function $S_0$ but not for $S_1$, and the level detection sensitivity was not sufficient to detect other than exceptionally strong $p$ levels. We were able to assign $J$ values to 14 $s$ levels of ${}_{}{}^{183}{}_{}{}^{}\mathrm{W}$. The 41 observed ${}_{}{}^{182}{}_{}{}^{}\mathrm{W}$ levels to 2.65 keV and the 52 ${}_{}{}^{183}{}_{}{}^{}\mathrm{W}$ levels to 701 eV seem to be pure complete $s$ populations, being fitted excellently by the Wigner nearest neighbor spacing theory and the Porter-Thomas reduced neutron width distribution. The orthogonal ensemble (OE) theory was found to be in good agreement with the ${}_{}{}^{182}{}_{}{}^{}\mathrm{W}$ and ${}_{}{}^{183}{}_{}{}^{}\mathrm{W}$ data. The ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$ level set to ∼2.6 keV also seems to be an essentially complete, pure, $s$ population sample. While it agreed within statistical limits to the above statistical theories, it gave poorer discrimination against alternate theories. Tests suggested that a few $s$ levels in ${}_{}{}^{186}{}_{}{}^{}\mathrm{W}$ had been missed to ∼2.6 keV. The ${10}^4{S}_o$ values are 2.40 ± 0.31, 1.65 ± 0.32, 2.35 ± 0.24, and 2.23 ± 0.27 for 182, 183, 184, and 186, respectively. The $〈D〉$ values for $s$ populations are 66.3 ± 3.2 eV (182), 13.2 ± 0.7 eV (183), 81.3 ± 5.1 eV (184), and 90 ± 7 eV (186). A useful and accurate method for evaluating the Doppler-broadening integrals is described.

Results are presented of measurements of the total cross section vs energy which was measured to 320 keV for pure metallic sodium. $R$-matrix fits were made to the seven prominent observed resonances. The best-fit parameters for ($E_0,\Gamma ,J,l$) for each resonance are: (2.850, 0.400, 1, 0); (53.15, 1.08, 2, 1); (199.0, 4.5, 1, 0); (212.5, 15, 0, 1); (238, 3.9, 2, 1); (242, 3.5, 0, 1); (297, 1.8, 2, 0), where $E_0$ and $\Gamma$ are in keV. Three levels are assigned to be $s$ levels, and four to be $p$ levels. This gives ${10}^4{S}_0=0.24\left(1_{-0.58\mathrm{}}^{+1.91\mathrm{}}\right)$ and ${10}^4{S}_1=2.06\left(1_{-0.39\mathrm{}}^{+0.77\mathrm{}}\right)$. The $S_1$ evaluation includes the presence of weak $p$ levels seen in capture measurements by others.

Results are presented of high-resolution transmission measurements using pure natural K metal samples. The measured total $\sigma$ vs $E$ to 400 keV is given, and resonance parameter evaluations are given for 65 resonances below 200 keV. The isosopte assignments, $A=39\mathrm{} or 41$, are mainly based on recent unpublished measurements of Good and Harvey at the Oak Ridge electron linear accelerator using separated K isotope samples. Values of level strengths, $\mathrm{ag}{\Gamma }_n$, are mainly based on transmission dip area analysis, which with evidence from the resonance shape and peak cross sections permits assignment of $l$ and $J$ for most resonances, and $A$ for many of the resonances not identified in the separated isotope measurements. We obtain for the $s$ and $p$ strength functions: $10{}_{}{}^4{}_{}{}^{}S_0^{}{}_{}{}^{}=\left({0.66}_{-0.30\mathrm{}}^{+0.63\mathrm{}}\right),\left({0.78}_{-0.41\mathrm{}}^{+1.08\mathrm{}}\right)$, and $10{}_{}{}^4{}_{}{}^{}S_1^{}{}_{}{}^{}=\left({1.8}_{-0.5\mathrm{}}^{+0.7\mathrm{}}\right) \mathrm{and} \left({2.4}_{-0.8\mathrm{}}^{+1.3\mathrm{}}\right)$ for ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ and ${}_{}{}^{41}{}_{}{}^{}\mathrm{K}$, respectively.

The deformation effect $\Delta {\sigma }_{\mathrm{def}}$ in the ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}+n$ total cross section has been measured at neutron energies of 1.0, 1.2, 1.4, 1.6, 2.0, and 15.9 MeV employing a single-crystal target with 16% nuclear alignment. The average of the five measurements at energies between 1 and 2 MeV was $\Delta {\sigma }_{\mathrm{def}}=-259\mathrm{}\pm 41$ mb; at 15.9 MeV, $\Delta {\sigma }_{\mathrm{def}}=-37\mathrm{}\pm 42$ mb. These results, when interpreted using the first-order distorted-wave Born-approximation theory, imply a value of 0.39 ± 0.06 b for the quadrupole moment of ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$, which is in good agreement with the result of other techniques.

[NUCLEAR MOMENTS ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$; measured deformation effect; deduced $q$, aligned ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$.]

Ground-state analog transitions in the (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $t$) scatterings are adequately described by introducing shell effects into both the real and imaginary part of the asymmetry potential.

The imaginary part of the optical potential of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ for neutrons is obtained numerically under the assumption that ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ is a spherical nucleus characterized by a vibrational spectrum built up from quadrupoles and/or octupoles. The "intermediate" compound states of the $n-{}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ system were generated from a strong particle-vibration coupling interaction between the target and the neutron. The calculations were carried out under the assumption that only elastic scattering was permissible. When compared with phenomenological potentials our results show a stronger dependence on the structure of the compound nucleus. Some of the characteristics of the $A+1\mathrm{}$ system, such as the energies of the single-particle states and their splitting into the intermediate compound states, show up clearly through the angular dependence of the Fourier transforms $W(\overrightarrow{\mathrm{k}},{\overrightarrow{\mathrm{k}}}^{\prime })$ of the imaginary potential.

A simple formulation of the coupled-channel Born approximation is presented, for the case where the spin-dependent term in the optical potential can be ignored. The formalism is particularly useful in reducing the computer time required when numerical calculations are carried out for one-particle transfer reactions.

The formalism is then applied to calculate one-particle pickup and stripping reactions such as ($p,d$), (${}_{}{}^3{}_{}{}^{}\mathrm{He},\alpha$), ($d,t$), and (${}_{}{}^3{}_{}{}^{}\mathrm{He},d$), all leading to the 1.61-MeV ${\frac{7}{2}}^{+}$ and the 3.4-MeV ${\frac{9}{2}}^{+}$ states, together with the ${\frac{5}{2}}^{+}$ ground states in mass-25 nuclei. It is shown that the observed cross sections are all well reproduced by the Coupled-Channel-Born-approximation calculations.

The (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$) and (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$) reactions on targets of ${}_{}{}^{90,91,94}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$, and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$ have been investigated with a 104-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ beam from the Berkeley 88-in. cyclotron. Spectra for the (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$) reaction (leading to the ground states of ${}_{}{}^{90,93}{}_{}{}^{}\mathrm{Zr}$) and for the (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$) reaction on ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ at 78 MeV were also obtained. Outgoing heavy ions were detected in the focal plane of a magnetic spectrometer with a Borkowski-Kopp type position-sensitive proportional counter backed by a plastic scintillator. The (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$) and (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$) data indicate a preference for high-angular-momentum transfer similar to (but less pronounced than) that shown by the ($\alpha ,t$) and ($\alpha$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$) reactions on the same targets. No evidence for a multistep excitation of core-excited states is apparent from the present data.

Reduced matrix elements $B (M2;1h_{\frac{11}{2}}\to 1g_{\frac{7}{2}})=11.0\mathrm{}\pm 0.6{\left(\frac{e\hslash }{2MC}\right)}^2$ fm${}_{}{}^2{}_{}{}^{}\mathrm{and}$ $B (E3;1h_{\frac{11}{2}}\to 2d_{\frac{5}{2}})=(11.6\mathrm{}\pm 2.2)\times {10}^3{e}^2$ ${\mathrm{fm}}^6$ in ${}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}$ were obtained by studying $\gamma$ rays following the ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}(\alpha ,2n){}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}$ reaction. Detailed analysis of the $M2$ and $E3$ transitions in nuclei with neutron number $\simeq 82$ gave effective coupling constants $g \frac{{}_{}{}^{\mathrm{eff}}{}_{}{}^{}\left(M2\right)}{g\left(M2\right)}\simeq 0.22$, and $g \frac{{}_{}{}^{\mathrm{eff}}{}_{}{}^{}\left(E3\right)}{g\left(E3\right)}\simeq 3$. They were analyzed in terms of the spin-isospin core polarization and the octupole core polarization, respectively.

Methods are developed for determining the properties of low-lying states in odd-mass systems with a residual interaction of the $0^{+}$ particle-particle form. Using matrix elements obtained from a surface-peaked $\delta$ interaction, the methods of this paper are applied to an analysis of states in ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{237}{}_{}{}^{}\mathrm{U}$. The results are compared with equivalent pairing-force model calculations. Substantial differences, on the order of 300 keV, are found in the single-particle energy level spectra deduced from the two residual interactions.

[NUCLEAR STRUCTURE: Quasiparticles; residual interactions; ${}_{}{}^{235,237}{}_{}{}^{}\mathrm{U}$ calculated levels.]

The ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}({}_{}{}^3{}_{}{}^{}\mathrm{He},d){}_{}{}^{97}{}_{}{}^{}\mathrm{Nb}$ reaction was studied with 22-MeV ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ particles. Experimental angular distributions were analyzed by use of distorted-wave Born-approximation calculations to determine $l$ values and spectroscopic factors. The results are compared with previous data on reactions and $\beta$ decay. The proton configurations of ${}_{}{}^{97}{}_{}{}^{}\mathrm{Nb}$ are examined in comparison with neighboring niobium nuclei and recent theoretical results.

[NUCLEAR REACTIONS ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}({}_{}{}^3{}_{}{}^{}\mathrm{He},d)$, $E=22\mathrm{}$ MeV; measured $\sigma (E_d,\theta )$; deduced ${}_{}{}^{97}{}_{}{}^{}\mathrm{Nb}$ levels, $l$, $j$, $G_{\mathrm{lj}}$.]

The elastic and inelastic scattering of 72.2-MeV ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ ions from ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ were studied. The angular distributions for transitions to the $3^{-}$, $5^{-}$, $2^{+}$, and $4^{+}$ states at 2.61, 3.20, 4.10, and 4.31 MeV, respectively, show pronounced effects due to interference between Coulomb and nuclear excitation. The data are well reproduced by distorted-wave calculations provided that the phase of the nuclear excitation form factor is altered by 5° from that given by the collective model.

[NUCLEAR REACTIONS ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$(${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$) and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$(${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}_{}^{*}{}_{}{}^{}$), $E_{{11}_{\mathrm{B}}}=72.2\mathrm{}$ MeV, measured $\sigma \left(\theta \right)$. Studied Coulomb and nuclear interference. DWBA analysis. Enriched target.]

A dispersion term which is attributed to interference between internal conversion following nuclear resonance absorption of $\gamma$ rays and the photoelectric effect has been observed in ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ Mössbauer absorption spectra measured as a function of Au-metal-absorber thickness. From line-shape analysis which accounts for absorber thickness, the amplitude of the dispersion term is found to be $\xi =(-4.14\mathrm{}\pm 0.17)\times {10}^{-3\mathrm{}}$. Neglect of the dispersion term leads to an apparent thickness-dependent isomer shift, whereas inclusion of the dispersion term gives isomer shifts properly independent of thickness.

[RADIOACTIVITY ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, $E_{\gamma }=77.3\mathrm{}$ keV; measured Mössbauer effect. Deduced interference effect in absorption spectra.]