The radioactive decays of ${}_{}{}^{21}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{23}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{23}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Ne}$, and ${}_{}{}^{31}{}_{}{}^{}\mathrm{S}$ have been studied using Ge (Li) and plastic scintillation detectors to measure $\gamma$ and $\beta$ rays. ${}_{}{}^{21}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{23}{}_{}{}^{}\mathrm{Ne}$, and ${}_{}{}^{24}{}_{}{}^{}\mathrm{Ne}$ were formed by bombarding a neon target with 3-MeV deuterons or tritons, followed by gas transfer to a remote counting station. ${}_{}{}^{23}{}_{}{}^{}\mathrm{Mg}$ and ${}_{}{}^{31}{}_{}{}^{}\mathrm{S}$ were made in ($p,n$) reactions using 10-MeV protons from an MP tandem Van de Graaff together with a rabbit target-transfer facility. The following half-lives (in sec) were obtained: ${}_{}{}^{21}{}_{}{}^{}\mathrm{Na}$, 22.55 ± 0.10; ${}_{}{}^{23}{}_{}{}^{}\mathrm{Ne}$, 37.24 ± 0.12; ${}_{}{}^{23}{}_{}{}^{}\mathrm{Mg}$, 11.36 ± 0.04; and ${}_{}{}^{31}{}_{}{}^{}\mathrm{S}$, 2.605 ± 0.012. Relative $\beta$-ray intensities were derived from the measured $\gamma$-ray intensities. The various branching results are in reasonable agreement with previous work except for ${}_{}{}^{21}{}_{}{}^{}\mathrm{Na}$ whose measured ${\beta }^{+}$ branch of 5.1 ± 0.2% to the 350-keV state of ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$ is a factor of 2 larger than earlier reports. However, the result is in excellent agreement with an estimate by Wilkinson.

[RADIOACTIVITY ${}_{}{}^{21}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{23}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{23}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{31}{}_{}{}^{}\mathrm{S}$; measured $T_{\frac{1}{2}}$, $I_{\gamma }$; deduced $\beta$ branches, $log\mathrm{ft}$.]

Integrated excitation functions for the reactions ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}(\alpha ,p_0){}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$ and ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}(\alpha ,p_1){}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}_{}^{*}{}_{}{}^{}$ were measured over the energy range $E_{\alpha }=2.3-3.7\mathrm{}$ MeV. Absolute resonance strengths were determined for 30 new $p_1$ resonances and 9 new $p_0$ resonances. The corresponding stellar reaction rate $N_A<\sigma V>\mathrm{}$ is recalculated and found to be enhanced by a factor of 3 at $T_9=2\mathrm{}$ and by a factor of 4 at $T_9=3\mathrm{}$. A multiparameter analytic fit to the new $N_A<\sigma V>\mathrm{}$ as a function of temperature over the range $T_9=0.3-5.0\mathrm{}$ is given. The enhanced rate was incorporated in a nucleosynthesis code and the resulting change in ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ and ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$ abundances at selected temperatures is discussed.

[NUCLEAR REACTIONS ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}(\alpha ,p)$, $E=2.3-3.7\mathrm{}$ MeV; measured excitation function and deduced resonant strengths for $p_0$ and $p_1$ proton groups; NaCl target. Calculated new thermonuclear reaction rate.]

We give here an approach to the angular momentum reduction that is tailed to be appropriate for the multichannel structure of the three-body problem. Wherever possible we work directly with the physical scattering amplitudes. We obtain concrete partial-wave expansions of elastic, rearrangement, and breakup amplitudes. For these amplitudes we obtain a coupled two-variable integral equation. The effects of parity, time reversal, and rotational invariance are fully discussed. Finally, we provide expressions for the multichannel partial-wave cross sections, asymptotic coordinate-space wave functions, off-shell unitarity, and the partial-wave version of the optical theorem as well as phase-shift parametrizations of the amplitudes.

Using a Green's function formalism, the quasiparticle self-energy in a finite Fermi system is derived from the particle-particle-hole response function with the assumption that particle-particle and three-body correlations are negligible. An approximate calculation of the self-energy includes the usual core-polarization diagram, a backwards exchange diagram with ground-state correlations, and higher-order diagrams which correct for exclusion-principle violations in the propagation of the quasiparticle and the microscopic phonon. Intermediate lines in the self-energy are described self-consistently, thereby including multiple-phonon core excitations. It is shown that the equation for the self-energy may be solved by matrix diagonalization by coupling the even- and odd-nuclear eigenmodes. Renormalized phonons are calculated by taking into account the distribution of quasiparticle strength by quasiparticle-phonon coupling in the solution of the Bethe-Salpeter equation. The self-energy and phonon are calculated self-consistently.

The form, as determined by the coherence formalism, of the final-state-interaction (fsi) amplitude for three-particle breakup reactions is derived from the Faddeev equations in the case of $n-d$ breakup. A parametrization of the Faddeev amplitudes in the fsi region is presented and interpreted. The detailed analytic form of fsi differential cross sections is obtained, showing that the most important fsi parameters are the two-particle scattering length and an effective target size, which exhibits dilation effects. Analysis of experiments with the theory implies charge symmetry of nuclear forces.

[NUCLEAR REACTIONS $n(d,nn)p$; final-state-interaction theory. Coherence formalism, Faddeev-amplitude parametrization, initial-state interaction.]

A useful way to characterize the hole-energy spectrum excited in a direct particle-removal reaction like ($p,2p$) or ($e,e^{\prime }p$) is through the centroid or mean removal energy. We derive the rules for computing this quantity in a linked-cluster expansion, and give some examples. We demonstrate the close relation of the mean removal energy to Brandow's self-consistent orbital energy, and discuss briefly the connection with Green's function theory.

[NUCLEAR STRUCTURE Linked-cluster theory of mean or centroid removal energies measured in ($p,2p$) or ($e,e^{\prime }p$); applications and relation to other hole energies.]

Possible deviations from the Alaga rules based on the use of projection-integral wave functions are investigated. It is shown that while such deviations, in principle, exist, they identically vanish in the region of heavy deformed nuclei, if it is assumed that these nuclei can be described by "semirigid" intrinsic wave functions.

[NUCLEAR MOMENTS Deformed nuclei; calculated $B\left(E2\mathrm{}\right)\mathrm{}$ deviations. Projection integral wave functions.]

Measurements of the (${\pi }^{+},p$) reaction on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have been made for 70-MeV pions. A magnetic spectrometer was used to momentum analyze the pion beam while thick Nal(T1) detectors were used to determine the proton energy. The experimental resolution was 3 MeV. Data from the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ targets were taken around a laboratory scattering angle of 25°. The number of (${\pi }^{+},p$) events from these nuclei was not significantly greater than background contributions, and therefore upper limits on the corss section are presented. Data from the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({\pi }^{+},p){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ reaction were obtained at proton emission angles of 20 and 32° (lab), while for ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, measurements were made over the angular range from 33 to 90°. Our experimental cross section for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({\pi }^{+},p){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ reaction, obtained by integrating over ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ excitation energies from 0 to 8 MeV, did not agree well with existing theoretical predictions. Results from the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}({\pi }^{+},p){}_{}{}^5{}_{}{}^{}\mathrm{Li}$ reaction indicated excitation of the $p_{\frac{1}{2}}$ state of ${}_{}{}^5{}_{}{}^{}\mathrm{Li}$. The cross section for this reaction decreased rapidly for emission angles less than 60°, while at larger angles the cross section was constant within the measured range.

[NUCLEAR REACTIONS ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}({\pi }^{+},p)$, $E=70\mathrm{}$ MeV, measured $\sigma \left(\theta \right)$.]

A kinematically complete experiment that examines the ${}_{}{}^2{}_{}{}^{}\mathrm{H}(p,pp)n$ reaction at several quasifree angles has been performed. The results are compared with calculations performed with a program based on the code of Ebenhöh that solves the Faddeev equations with separable two-body potentials. The calculations are compared with two other programs that use a different integration contour, and the numerical differences are found to be small. The Ebenhöh code is used with three $S$-wave Yamaguchi potentials. Two of the potentials differ primarily in their predictions of the singlet $p-p$ scattering length. The third potential fits the two-body $np$ and $pp$ scattering data below 30 MeV. The potentials give generally good fits to the breakup data, but do not provide a precise fit to the angular distribution for the quasifree peaks. The potentials themselves differ by about 30% in the predicted quasifree peaks. The calculations explictly show that interference effects are important. It is concluded that a precise fit to the $N-N$ data is not sufficient alone to guarantee a fit to quasifree deuteron breakup data and that the Yamaguchi form factor is inadequate for this purpose.

[NUCLEAR REACTIONS ${}_{}{}^2{}_{}{}^{}\mathrm{H}\mathrm{}(p,pp)\mathrm{}$, $E=23\mathrm{}$ MeV; measured ${}_{}{}^3{}_{}{}^{}d\sigma$, quasielastic angles. Faddeev calculation, 3 potentials, 3 codes.]

The proton spectrum over the angular interval of 0 to 10 mrad from the interactions of 29.4-GeV nitrogen on carbon has been calculated. The differential cross section for the emission of protons indicates that there is a significant number of emitted protons with energies greater than the energy per nucleon of the incident projectile (2.1 GeV). A description of the calculational method is included.

[NUCLEAR REACTIONS ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}({}_{}{}^{12}{}_{}{}^{}\mathrm{C},p)$, $E=29.4\mathrm{}$ GeV; calculated $\sigma \left(E_p\right)$, $\theta =0-10\mathrm{}$ mrad.]

Measurements of $\gamma$ rays from the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}(n,n^{\prime }\gamma )$ reaction have been performed with 0.2-1.7-MeV incident neutrons. The measured 110- and 197-keV level excitation functions, magnetic substate populations, and $\gamma$-ray angular distributions are generally consistent with compound-nuclear calculations. Although the experimental values of the 197-keV level excitation function are also consistent with a 15% direct-interaction component, the corresponding magnetic substate populations and 197-keV $\gamma$-ray angular distributions are not sensitive to this component.

[NUCLEAR REACTIONS ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}(n,n^{\prime }\gamma )$, $E=0.2-1.7\mathrm{}$ MeV; measured $\sigma \mathrm{}\left(E\right)\mathrm{}$, $\sigma (E=1.3\mathrm{}$ MeV,$\theta$); deduced magnetic substate populations, calculated $\sigma (E,\theta )$, magnetic substate populations; DWBA and CN analysis.]

The equivalent photon cross sections were extracted from deuteron electrodisintegration measurements over an energy range of 17 to 28 MeV. Proton angular distributions were measured at 12 photon energies and the total cross section determined with an experimental uncertainty of approximately ≲6%. The differential cross section at 90 ° c.m. was also measured. Satisfactory agreement is found between deuteron photodisintegration theory and our measurements. A comparison with other recent ($\gamma ,p$) cross section measurements is made.

[NUCLEAR REACTIONS ${}_{}{}^2{}_{}{}^{}\mathrm{H}\mathrm{}(e,p)\mathrm{}{e}^{\prime }n$, measured $\sigma (E_p,\theta )$, extracted ${}_{}{}^2{}_{}{}^{}\mathrm{H}(\gamma ,p)n$.]

The relativistic Hartree formalism for nuclei is extended to include the exchange potentials which result from various kinds of one-boson-exchange interactions. A numerical simplification is presented which uncouples the relativistic Hartree-Fock equations and enables local (though state-dependent) single-particle potentials to be defined for the exchange interactions. Calculations are presented for a vector-scalar nucleon-nucleon force model. Comparison of these calculations with Hartree calculations (using the same model) indicates that the exchange terms contribute a net attraction of about 1.5 MeV per particle in light nuclei, while rms radii are reduced by about 0.03 fm. A study is also made of the exchange potentials resulting from the pseudoscalar part (one-pion-exchange) of the nucleon-nucleon interaction. These terms appear to be important, although self-consistent calculations are not possible in the present framework due to numerical instabilities induced by the pseudoscalar term. The instabilities appear to be related to an incorrect enhancement of the effects of virtual $N-\overline{N}$ pair creation which is present in the coordinate space relativistic one-pion-exchange potential.

[NUCLEAR STRUCTURE ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$; calculated binding energies, eigen-values, charge radii, exchange potentials. Relativistic Hartree-Fock method, spherical nuclei.]

Energy-independent and energy-dependent analyses are given for the proton-proton scattering data from 1 to 500 MeV. These analyses are similar to those of the Livermore series, but a number of modifications have been made, particularly in the low-energy representation. First, the range of the analyses has been extended by 50 MeV (i.e., from 450 to 500 MeV) and provisions have been made to include total cross sections in the analyses. This and new data additions have resulted in a 20% expansion of the data base. The other modifications concern the low-energy data and the representation bases. To help alleviate normalization difficulties with the low-energy data, the normalization errors of all experiments in the 0- to 10-MeV energy range were floated. The $S$-wave scattering-length and effective-range parameters were adjusted to give the best fit to the data, and the energy-dependent representation was modified to account for low-energy Coulomb effects. A 28-parameter energy-dependent solution is obtained which is quite good, with ${\chi }^2=1052\mathrm{}$ for 1233 data. This is a definite improvement over the Livermore result, but the phase shifts in the 50- to 400-MeV range are virtually unchanged (with the exception of the ${}_{}{}^3{}_{}{}^{}F_4^{}{}_{}{}^{}$ and ${}_{}{}^1{}_{}{}^{}G_4^{}{}_{}{}^{}$ phases) despite the modifications to the bases functions, a strong indication that the data place strong restrictions on the phases.

[NUCLEAR STRUCTURE energy-dependent, energy-independent phase-shift analyses of 1-500-MeV $p-p$ scattering data.]

Theoretical expressions for the differential cross section of symmetric, coplanar ($p,2p$) quasifree scattering on ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are derived in the plane-wave impulse approximation with full account given to the spin effects of the nucleon-nucleon interaction and the nuclear bound states. The phenomenological $M_{12}$ matrix is utilized as are correlated functions and Eckart parametrizations of the distribution functions for the light nuclei. Shape fits to experimental data for the Eckart parametrizations are found to be extremely good although theory overpredicts the magnitudes of the cross sections. It is shown that an intuitive extension of the attenuation model of Rogers and Saylor is able to remove this latter discrepancy in ${}_{}{}^3{}_{}{}^{}\mathrm{He}\mathrm{}(p,2p)\mathrm{}{}_{}{}^2{}_{}{}^{}\mathrm{H}$. We also indicate the possible usefulness of our matrix elements in polarization studies.

[NUCLEAR REACTIONS ${}_{}{}^2{}_{}{}^{}\mathrm{H},{}_{}{}^{3,4}{}_{}{}^{}\mathrm{He}\mathrm{}(p,2p)\mathrm{}$, $E=20-160\mathrm{}$ MeV; calculated $\sigma$.]

Excitation functions and angular distributions of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(p,{\alpha }_0){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ for bombarding energies of 9.0 through 12.0 MeV have been measured in steps of 50 keV from 10 through 160°. Prominent structures are noted near excitations of 16.2, 17.2, and 17.8 MeV in ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$ and are observed to be composed of many sub-structures. Legendre polynomial fits to the angular distributions have been made. Corresponding structures are noted in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^3{}_{}{}^{}\mathrm{He},{\alpha }_0){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ reaction and comparisons are made with the $\alpha$-particle core-excited threshold-state model which had been applied to ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$.

[NUCLEAR REACTIONS ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(p,{\alpha }_0)$, $E=9.0-12.0\mathrm{}$ MeV; ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$ deduced resonances. $\theta =10-{160}^{\circ }$, $\Delta \theta ={10}^{\circ }$, $\Delta E=50\mathrm{}$ keV.]

The ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}(\alpha ,2\mathrm{}\alpha ){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ reaction has been measured at symmetric and asymmetric sets of angles at $E_{\alpha }=78.6\mathrm{}$ MeV. The data indicate that quasifree $\alpha -\alpha$ scattering and, consequently, $\alpha$ clustering plays a dominant role for pairs of angles favoring quasifree scattering. The data have been compared with the plane-wave impulse approximation using a radial cutoff. This calculation does not give a good fit to data for non-quasifree angles. The reaction goes predominantly to the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ground state with a small yield to the 6.92-7.12-MeV doublet in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$.

[NUCLEAR REACTIONS ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}(\alpha ,2\mathrm{}\alpha ){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, $E=78.6\mathrm{}$ MeV; measured ($E_L,E_R,{\theta }_L,{\theta }_R$). PWIA analysis.]

An analysis of the ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}({}_{}{}^3{}_{}{}^{}\mathrm{He},p){}_{}{}^{28}{}_{}{}^{}\mathrm{Al}$ reaction at a bombarding energy of 18 MeV has enabled the identification of 80 levels in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Al}$ below $E_x=8.65\mathrm{}$ MeV. A distorted-wave analysis of the angular distributions of these transitions has led to unique spin-parity assignments for 8 levels. Limits have been set on the spins and parities of 17 states.

[NUCLEAR REACTIONS ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}({}_{}{}^3{}_{}{}^{}\mathrm{He},p)$, $E=18\mathrm{}$ MeV; measured $\sigma (E_p,\theta )$, enriched target. ${}_{}{}^{28}{}_{}{}^{}\mathrm{Al}$ deduced levels $L$, $J$, $\pi$.]

Excitation energies and nuclear lifetimes of states in ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ar}$ have been measured by employing the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}\mathrm{}(t,p)\mathrm{}{}_{}{}^{42}{}_{}{}^{}\mathrm{Ar}$ at a triton bombarding energy of 2.8 MeV. Protons were detected by an annular silicon surface barrier counter at an average angle of 174°, and coincident $\gamma$ rays were detected by a 20-cm${}_{}{}^3{}_{}{}^{}\mathrm{Ge}$(Li) counter positioned at angles of 30 and 120°. The extraction of nuclear lifetimes by the Doppler-shift-attenuation technique was made possible by the use of a solid argon target operated at 15 K. Experimental results for excitation energies (keV) and lifetimes (psec) are: 1208.2±0.3, ${3.8}_{-0.8\mathrm{}}^{+1.0\mathrm{}}$; 2486.7±0.6, 0.40±0.16; 2512.5±0.5, ${4.0}_{-1.2\mathrm{}}^{+3.1\mathrm{}}$; 3014.6±0.6, <0.12; 3096.4±0.6, >5; 3557.8±0.6, <0.09; 4006.1±0.6, 3.3±0.8; 4127.4±0.7, 1.4±0.3; 4287.0±0.7, <0.05; 4633.7±0.7, <0.05. The experimental results are in good agreement with the shell-model calculations of Gloeckner, Lawson, and Serduke.

[NUCLEAR REACTIONS ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}\mathrm{}(t,p)\mathrm{}$, $E_t=2.8\mathrm{}$ MeV; measured $\sigma (E_p,E_{\gamma },{\theta }_{\gamma })$. ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ar}$ deduced $E_x$, $I_{\gamma }$, ${\tau }_m$. Solid Ar target; Doppler shift attenuation.]

The reduction of the Doppler shift for several bound-state transitions in ${}_{}{}^{61}{}_{}{}^{}\mathrm{Cu}$ due to the intervening $\gamma$ cascades from the continuum was measured, using the Doppler-shift-attenuation method in a $p-\gamma$ coincidence arrangement that employed the ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}(\alpha ,p\gamma ){}_{}{}^{61}{}_{}{}^{}\mathrm{Cu}$ reaction at 19.7 MeV. It is found that the mean lifetimes of cascades that begin at the most probable excitation energy of ∼ 9.5 MeV in ${}_{}{}^{61}{}_{}{}^{}\mathrm{Cu}$ and populate the 2336.2-keV (9/$2^{-}$), 2611.8-keV (9/$2^{-}$), and 3015.6-keV (11/$2^{-}$) states are, respectively 0.29 ± 0.12, 0.19 ± 0.07, and 0.43 ± 0.14 ps. The mean lifetimes of the cascades feeding the above three states were found to increase with increasing total energy available for the cascades with an approximately linear dependence with slopes of 40 ± 22, 29 ± 12, and 69 ± 12, and 69 ± 20 fs/MeV. These results are consistent with an increase in the $\gamma$ multiplicity in the cascades with increasing total available cascade energy.

[NUCLEAR REACTIONS ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}(\alpha ,p\gamma ){}_{}{}^{61}{}_{}{}^{}\mathrm{Cu}$, $E_{\alpha }=19.7\mathrm{}$ MeV; measured $\overline{\tau }\left(E^{*}\right)$, the energy dependence of the mean lifetimes of the $\gamma$ cascades in ${}_{}{}^{61}{}_{}{}^{}\mathrm{Cu}$. Enriched targets, Ge(Li) $\gamma$ detectors, annular Si(Li) detector, Doppler-shift analysis of line shapes.]