Proton spectra from the reaction ${}_{}{}^7{}_{}{}^{}\mathrm{Li}\mathrm{}(t,p)\mathrm{}{}_{}{}^9{}_{}{}^{}\mathrm{Li}$ have been measured at triton energies of 15 and 19 MeV. Evidence is observed for new states in ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$ at excitation energies of 4.31±0.03, 5.38±0.06, and 6.41±0.02 MeV, having widths of 0.25±0.03, 0.6±0.1, and <0.1 MeV, respectively. Angular distributions were obtained at $E_t=15\mathrm{}$ MeV for the ground, 4.31-, and 6.41- MeV states. The shape of the ground-state distribution is similar to an $L=0\mathrm{}$ distorted-wave Born-approximation calculation, in agreement with the assignment $J^{\pi }={\frac{3}{2}}^{-}$ for the ground state of ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$. The relative magnitude of the cross section to the first excited state, when considered with other work, provides support for the assignment of $J^{\pi }={\frac{1}{2}}^{-}$.

The reaction ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(d,\gamma ){}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ has been studied over the deuteron energy range of 0.56-3.56 MeV. A pulsed deuteron beam and time-of-flight electronics have been utilized to separate deuteron-capture $\gamma$ rays from events due to neutrons and cosmic rays. From a graphical analysis of the excitation functions for the ground, first, and combined second and third excited states, two resonances have been identified corresponding to ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ excitation energies of 17.44±0.05 and 18.37±0.05 MeV. The first of these occurs at the same energy as a level in ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ found from other reactions. An interpretation in terms of $1s_{\frac{1}{2}}$ hole states is suggested. The overall behavior of the three excitation functions is used to justify a direct-capture reaction mechanism. Angular distributions were measured at 21 different deuteron energies. The near symmetry of the angular distributions about 90° and the peaking at 90° imply that a one-step deuteron-capture process is important for this reaction if the direct-capture mechanism is dominant. An appreciable forward peaking is observed for the first-excited-state angular distribution.

The mean lifetime of the 1.99-MeV ${\frac{7}{2}}^{-}$ level of ${\mathrm{S}}^{35}$ was determined by a measurement of the delayed coincidence between protons and $\gamma$ rays in the reaction ${\mathrm{S}}^{34}(d,p\gamma ){\mathrm{S}}^{35}$ at $E_d=4.48\mathrm{}$ MeV, with the result ${\tau }_m=1.47\mathrm{}\pm 0.07$ nsec. The $\gamma$ decay of the ${\frac{7}{2}}^{-}$, $T=\frac{3}{2}$ analog of this level at $E_x=7.55\mathrm{}$ MeV in ${\mathrm{Cl}}^{35}$ was examined in detail with large-volume Ge(Li) detectors and Ge(Li)-NaI(Tl) coincidence techniques. The $\gamma$-ray spectra obtained at the analog state, which appears as a well-known resonance at $E_p=1211\mathrm{}$ keV in the reaction ${\mathrm{S}}^{34}(p,\gamma ){\mathrm{Cl}}^{35}$, revealed the presence of several previously unknown transitions in addition to the known strong analog-to-antianalog $M1\mathrm{}$ transition to the ${\frac{7}{2}}^{-}$, $T=\frac{1}{2}$ level at 3.16 MeV. Examples are a crossover $M2\mathrm{}$ transition from the analog resonance to the ${\frac{3}{2}}^{+}$ ground state of ${\mathrm{Cl}}^{35}$ with a strength of 3.0 ± 0.8 Weisskopf units, a mixed $E1\mathrm{}-M2\mathrm{}$ transition ($\delta =0.44\mathrm{}\pm 0.12$) from the ${\frac{7}{2}}^{-}$ antianalog state to the ${\frac{5}{2}}^{+}$ level at 1.76 MeV, and a 160-keV transition between the antianalog state and the ${\frac{5}{2}}^{+}$ level at 3.00 MeV. Weak transitions which can be interpreted as members of cascades through levels in the region $E_x=4.3-5.7\mathrm{}$ MeV were also identified. It is shown that the $M1\mathrm{}$, $E2\mathrm{}$, $M2\mathrm{}$, and $E3\mathrm{}$ strengths of transitions connecting members of the system of parent, analog, antianalog, and ground states can be accurately reproduced by a simple model based upon an inert ${\mathrm{S}}^{32}$ core with active nucleons in the $d_{\frac{3}{2}}$ and $f_{\frac{7}{2}}$ orbits, with bare-nucleon $g$ factors for the magnetic transitions, and with reasonable effective charges for the electric transitions. The wave functions for the ${\frac{7}{2}}^{-}$ levels derived from this model are used to predict strengths of mirror transitions in ${\mathrm{Ar}}^{35}$ and ${\mathrm{K}}^{35}$.

The ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ca}\mathrm{}(d,t)\mathrm{}{}_{}{}^{45}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ca}(d,{}_{}{}^3{}_{}{}^{}\mathrm{He}){}_{}{}^{45}{}_{}{}^{}\mathrm{K}$ reactions have been investigated at an incident deuteron energy of 22.4 MeV. The angular distributions have been compared with distorted-wave calculations, and the spectroscopic strength has been extracted. The transitions to the ${\frac{3}{2}}^{-}$ levels of ${}_{}{}^{45}{}_{}{}^{}\mathrm{Ca}$ at 1.435 and 2.82 MeV were observed with a total strength $C^{2}S=0.3\mathrm{}$. The spectroscopic factor of the ground-state transition for the ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ca}(d,{}_{}{}^3{}_{}{}^{}\mathrm{He}){}_{}{}^{45}{}_{}{}^{}\mathrm{K}$ reaction was found to be $C^{2}S=1.5\mathrm{}\pm 0.3$. This suggests the probability of measurable core-excitation admixtures in the ground-state configuration of ${}_{}{}^{45}{}_{}{}^{}\mathrm{K}$.

Levels in ${\mathrm{Si}}^{29}$ were populated with the reaction ${\mathrm{Mg}}^{26}(\alpha ,n){\mathrm{Si}}^{29}$ and subsequent $\gamma$ radiation from the various levels was detected with a 37-${\mathrm{cm}}^3$ Ge(Li) $\gamma$-ray spectrometer. Beginning with the 4.08-MeV level, $\gamma$-ray angular distributions ($0^{\circ }\le {\theta }_{\gamma }\le {90}^{\circ }$) were measured at incident bombarding energies near threshold ($Q_0=0.033\mathrm{}$ MeV) for levels with excitation energies between 4.08 and 6.38 MeV. The target was a ${\mathrm{Mg}}^{26}$ metal foil, on the order of 0.5 ${\mathrm{m}\mathrm{g}/\mathrm{c}\mathrm{m}}^2$ thickness. Branching ratios and excitation energies of the various levels were deduced from $\gamma$-ray pulse-height distributions. $\gamma$-ray angular correlations obtained at $\alpha$ bombarding energies near threshold were treated as originating from residual nuclei having magnetic quantum numbers $\mathrm{}\left|m\right|=\frac{1}{2} \mathrm{and} \frac{3}{2}$. Analysis of these angular correlations in terms of level spin and $\gamma$-ray multipole mixing was then undertaken. Mean lifetimes (or limits) for these levels were determined using a variant of the Doppler-shift-attenuation method, which involves measurements of the attenuation for two targets of different stopping power. Both ${\mathrm{Mg}}^{26}$ foils and ${\mathrm{Mg}}^{26}$-Au alloy foils (10 at.% ${\mathrm{Mg}}^{26}$ and 90 at.% Au) were used. From these measurements, excitation energies (in keV), level spins, and lifetimes (in fsec) for these levels were deduced; these are, respectively, 4079.5 ± 0.4, $\frac{7}{2}$, 48 ± 8; 4740.5 ± 0.4, $\frac{5}{2} or \frac{9}{2}$, 45 ± 10; 4838.5 ± 0.8, ½ or $\frac{3}{2}$, <5; 4894.9 ± 0.6, $\frac{5}{2}$, 10 ± 3; 4932.6 ± 0.4, $\frac{3}{2}$, <10; 5254.1 ± 0.5, $\frac{9}{2}$, 100 ± 20; 5284.4 ± 0.7, $\frac{3}{2} or \frac{7}{2}$, <10; 5651.8 ± 0.7, $\frac{5}{2} or \frac{9}{2}$, 40 ± 15; 5810.7 ± 1.2, $\frac{7}{2}$, <20; 5946.3 ± 3.0, $\frac{3}{2}$, <30; 6106.6 ± 0.6, $\frac{3}{2} or \frac{5}{2}$, <8; 6190.7 ± 1.3, $\frac{3}{2}, \frac{5}{2}, or \frac{7}{2}$, <15; 6378.8 ± 3.0, ½ or $\frac{3}{2}$. Excitation energies and lifetimes of levels with $E_x<4.08\mathrm{}$ were determined as well. These are (keV, fsec) 1273.1 ± 0.2, 360 ± 70; 2027.6 ± 0.2, 360 ± 70; 2425.0 ± 0.4, 13 ± 3; 3066.9 ± 0.5, 20 ± 7; 3623.1 ± 0.3, 4000 ± 800. These data may be combined with the results of other investigations to arrive at a fairly complete level scheme for ${\mathrm{Si}}^{29}$ in the energy interval $0<\mathrm{}{E}_x$ (MeV) < 6.38, including a description of the electromagnetic decay properties. These properties are compared with model predictions of the properties of ${\mathrm{Si}}^{29}$.

Levels of ${\mathrm{Co}}^{56}$ up to 4.4-MeV excitation have been studied by the direct ${\mathrm{Ni}}^{58}(d,\alpha ){\mathrm{Co}}^{56}$ reaction at a deuteron energy of 17 MeV. Experimental resolution of 9 to 12 keV permitted investigation of many previously unknown states. ${\mathrm{Fe}}^{54}({\mathrm{He}}^3,p){\mathrm{Co}}^{56}$ spectra at $E_{{\mathrm{He}}^3}=18\mathrm{}$ MeV were taken in order to supplement an earlier low-resolution study at the same energy. The total experimental resolution obtained for this reaction was 16 keV and permitted investigation of previously unresolved doublets. Accurate (±0.3%) excitation energies were obtained for about 80 ${\mathrm{Co}}^{56}$ levels. ${\mathrm{Ni}}^{58}(d,\alpha ){\mathrm{Co}}^{56}$ angular distributions obtained by other investigators with 12- and 15-MeV deuterons had presented serious difficulties in the attempted analysis with distorted-wave Born-approximation (DWBA) calculations. At 17 MeV, given $L$ values led to characteristic shapes which could be recognized empirically and crudely fit by "conventional" DWBA curves. Stock et al. had shown in 1967 that finite-range corrections become less important and DWBA results more reliable for (${\mathrm{He}}^3,\alpha$) if $V_{{\mathrm{He}}^3}+V_n\approx V_{\alpha }$. We generalized this prescription to two-nucleon transfers and found similarly positive results, provided that the radii of all real wells were kept near $1.2A^{\frac{1}{3}}$ fm. With this "well-matching" prescription our microscopic DWBA calculations were improved to the point that the correlation of $L=0, 2, 4, 6$ curves to positive-parity states became unambiguous. In the study of individual ${\mathrm{Co}}^{56}$ states we used ($p,{\mathrm{He}}^3$) and (${\mathrm{He}}^3,t$) results of other investigators together with our own data to suggest $J^{\pi }$ assignments or narrow $J^{\pi }$ limits for 46 states. It was found particularly useful to investigate the $\frac{\sigma (d,\alpha )}{\sigma (p,{\mathrm{He}}^3)}$ ratio for given $L$ transfer. As expected on theoretical grounds, cross sections for $J^{+}$ (odd) levels showed large and nearly constant ratios. Ratios for transition strengths to known $J^{+}$ (even) states were significantly smaller and vanished for $T_{>}$ states. The properties of 15 low-lying levels could be correlated with those of states predicted in recent shell-model calculations by J. McGrory. The importance of two-particle-two-hole configurations in most of these states was demonstrated. Remaining discrepancies might be explained by a sizable four-hole-two-particle strength in ${\mathrm{Ni}}^{58}$(g.s).

Absolute cross sections for the formation of ${}_{}{}^{84}{}_{}{}^{}\mathrm{Rb}$, ${}_{}{}^{86}{}_{}{}^{}\mathrm{Rb}$, ${}_{}{}^{132}{}_{}{}^{}\mathrm{Cs}$, and ${}_{}{}^{136}{}_{}{}^{}\mathrm{Cs}$ in uranium and thorium interactions with 28.5-GeV protons were determined by $\gamma$-ray counting of chemically separated samples. The cross sections obtained are as follows: for thorium: ${}_{}{}^{84}{}_{}{}^{}\mathrm{Rb}$, 6.55 ± 0.37 mb; ${}_{}{}^{86}{}_{}{}^{}\mathrm{Rb}$, 6.75 ± 0.37 mb; ${}_{}{}^{132}{}_{}{}^{}\mathrm{Cs}$, 1.30 ± 0.06 mb; ${}_{}{}^{136}{}_{}{}^{}\mathrm{Cs}$, 1.13 ± 0.07 mb; for uranium: ${}_{}{}^{84}{}_{}{}^{}\mathrm{Rb}$, 6.88 ± 0.33 mb; ${}_{}{}^{86}{}_{}{}^{}\mathrm{Rb}$, 7.27 ± 0.34 mb; ${}_{}{}^{132}{}_{}{}^{}\mathrm{Cs}$, 2.10 ± 0.10 mb; ${}_{}{}^{136}{}_{}{}^{}\mathrm{Cs}$, 2.64 ± 0.15 mb.

Nearly monochromatic photons from positron annihilation in flight have been used to measure photoneutron cross sections for ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ and ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$ in the giant-resonance region. The shape of the giant resonance of each of these nuclei is rather broad, with less striking intermediate structure than in most neighboring $\mathrm{sd}$-shell nuclei. In ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ the total cross section rises to approximately 10 mb at 17.5 MeV and remains essentially constant up to 25 MeV. In ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$ the total cross section reaches a peak of 28 mb at 23.1 MeV and falls to approximately half that magnitude at the upper energy limit of the experiment (29 MeV). In both nuclei the ($\gamma ,2n$) cross section appears to rise slowly above threshold but does not exceed 1 mb within the energy limits of the experiment. The integrated cross sections for ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ and ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$ are 119 and 249 MeV mb, respectively; the bremsstrahlung-weighted integrated cross sections are 5.7 mb for ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ and 11.7 mb for ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$.

A Ge(Li) $\gamma$-ray spectrometer and a Si(Li) electron spectrometer were standardized for measurements of internal—conversion coefficients using $\gamma$ transitions of well-known ${\alpha }_K$ and ${\alpha }_L$ values from standard sources. The internal—conversion coefficients of four $\gamma$ transitions in ${}_{}{}^{81}{}_{}{}^{}\mathrm{Br}$ and one in ${}_{}{}^{81}{}_{}{}^{}\mathrm{Se}$ have been measured. The results for the conversion coefficients are as follows: ${}_{}{}^{81}{}_{}{}^{}\mathrm{Se}$, 103 keV: ${\alpha }_K=7.1\mathrm{}\pm 0.3$, ${\alpha }_L=1.6\mathrm{}\pm 0.3$; ${}_{}{}^{81}{}_{}{}^{}\mathrm{Br}$, 178 keV: ${\alpha }_K<0.05\mathrm{}$, ${\alpha }_L<0.003\mathrm{}$; 260 keV: ${\alpha }_K=0.038\mathrm{}\pm 0.001$, ${\alpha }_L=0.005\mathrm{}\pm 0.002$; 276 keV: ${\alpha }_K=0.009\mathrm{}\pm 0.001$, ${\alpha }_L=0.002\mathrm{}\pm 0.001$; 290 keV: ${\alpha }_K=0.012\mathrm{}\pm 0.001$, ${\alpha }_L=0.002\mathrm{}\pm 0.001$. The multipolarities are deduced to a fair degree of certainty.

The analog resonances of some low-lying states of ${}_{}{}^{69}{}_{}{}^{}\mathrm{Zn}$ have been investigated using the triple-angular-correlation geometry of Goldfarb and Seyler for the reaction ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}(p,p_1^{\prime }\gamma )-{}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}_{}^{*}{}_{}{}^{}$ (1.08 MeV). Excitation functions for elastic and inelastic protons ($0^{+}$, ground state; $2^{+}$, 1.08 MeV; $0^{+}$, 1.66 MeV; $2^{+}$, 1.88 MeV) have been measured at 90, 120, 130, and 160°. The following spin and parity assignments have been made for the states in ${}_{}{}^{69}{}_{}{}^{}\mathrm{Zn}$: 0.835 MeV, ${\frac{3}{2}}^{-}$; 0.872 MeV, ${\frac{5}{2}}^{+}$, 1.634 MeV, ${\frac{5}{2}}^{+}$; 1.696 MeV, ${\mathrm{½}}^{+}$; 2.262 MeV, ${\mathrm{½}}^{+}$; 2.403 MeV, ${\frac{5}{2}}^{+}$; 2.554 MeV, ${\frac{5}{2}}^{+}$; and 2.669 MeV, ${\mathrm{½}}^{+}$.

Measurements of Doppler shifts of $\gamma$ rays from nuclei recoiling in gas are described. Mean lives of the 0.87-MeV state in ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$, of the 0.58- and 0.97-MeV states in ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$, and of the 0.41-, 0.93-, 1.32-, and 1.41-MeV states in ${}_{}{}^{55}{}_{}{}^{}\mathrm{Fe}$ produced by ($d,p$) reactions were obtained from these Doppler shifts. The effect on these mean lives of a variation in the deuteron current has been investigated. Finally, the known mean lives of the 0.87-MeV state in ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ and the 0.58-MeV state in ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$ were used, together with the measured Doppler shifts, to obtain information concerning the slowing down of ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$ ions in krypton gas.

The energy dependence of the reorientation effect has been investigated using ${\mathrm{O}}^{16}$ and ${\mathrm{S}}^{32}$ ions incident on ${\mathrm{Fe}}^{56}$ nuclei. The influence of nuclear interference on the reorientation effect was observed before it could be detected on the elastic cross section, and exhibited an angular dependence similar to that expected for the reorientation effect. It was found that an appropriate separation of projectile and target nuclei was given by $2a=R_0({A_1}^{\frac{1}{3}}+{A_2}^{\frac{1}{3}})+\Delta$, where $R_0=1.6\mathrm{}$ fm and $\Delta \ge 3.5$ fm. The static quadrupole moment of the 0.847-MeV $2^{+}$ state in ${\mathrm{Fe}}^{56}$ was measured to be $Q_{22}=-0.23\mathrm{}\pm 0.03 \mathrm{b}$, while the rotational value is given by $\left|Q_R\right|=0.276\mathrm{} \mathrm{b}$.

Properties of positive-parity states of nuclei with $A=30-35\mathrm{}$ have been calculated in a shell-model space which encompasses all Pauli-allowed basis vectors of all configurations ${\mathrm{}\left(0s\right)\mathrm{}}^4{\mathrm{}\left(0p\right)\mathrm{}}^{12}{\left(0\mathrm{}{d}_{\frac{5}{2}}\right)}^{n_1}{\left(1\mathrm{}{s}_{\frac{1}{2}}\right)}^{n_2}{\left(0\mathrm{}{d}_{\frac{3}{2}}\right)}^{n_3}$ for which $n_1\ge 10$. Two different empirical Hamiltonians, one of a $\delta$-function form, were used. Calculated energies and spectroscopic factors are in good agreement with an extensive body of experimental data. The model wave functions also yield satisfactory agreement with many available experimental data on electric quadrupole observables if effective charges of $0.5e$ are added to the proton and neutron. The model predictions for magnetic dipole observables are generally in qualitative agreement with experimental observations, but inconsistencies between theory and experiment are more noticeable in this area.

The energy spectra of nuclear fragments produced by the interaction of 5.5-GeV protons with silver were determined at several laboratory angles by means of $\frac{\mathrm{dE}}{dx-E}$ measurements with semiconductor-detector telescopes. Individual isotopes of the elements from hydrogen to nitrogen were resolved. From oxygen to silicon the elements were determined without isotopic separation. For the case of the isotopes of He through Be enough of the evaporation-like energy spectra were recorded so that it was possible to perform integrations to obtain angular distributions and total cross sections. For elements above beryllium, an experimental cutoff on the low-energy side precluded these integrations, and only the high-energy portions of the spectra were recorded. The energy spectra of the neutron-deficient isotopes differ from the others in that the high-energy parts of the spectra are more pronounced and flatter, and the angular distributions are more forward-peaked.

Some of the energy spectra were fitted with calculated curves based on the isotropic evaporation of fragments from an excited nucleus moving along the beam axis. The apparent Coulomb barriers obtained from this analysis were about one half the nominal Coulomb barriers, and the apparent nuclear temperatures fell in the 8-11-MeV range. However, no one temperature could fit the entire energy range, and for the highest-energy fragments observed at 90° the apparent temperature rose to 20 MeV or higher. From the forward-backward shifts of the most probable energy it was deduced that the average velocity of the moving system emitting Li and Be fragments is $0.008c$. However, all of the data are more forward-peaked in intensity than can be explained by the simple two-step model. The energy analysis carried out on these new data is compared with those given in the literature for silver targets or emulsions bombarded with protons, cosmic rays, pions, kaons, and other particles. Comparisons are made of these results with those obtained in an earlier study of fragments from a uranium target.

The reactions ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}\mathrm{}(d,p)\mathrm{}{}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}\mathrm{}(d,p)\mathrm{}{}_{}{}^{33}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}\mathrm{}(d,p)\mathrm{}{}_{}{}^{37}{}_{}{}^{}\mathrm{Ar}$ were studied at an incident deuteron energy of 18.00 MeV. Some ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}\mathrm{}(d,p)\mathrm{}{}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ data were also obtained at an incident deuteron energy of 21.00 MeV. Angular distributions were obtained for proton groups leading to states in the residual nuclei ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{33}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ar}$ with excitation energies up to approximately 8 MeV. With the use of distorted-wave Born-approximation (DWBA) analyses, spectroscopic factors were obtained for all ($d,p$) transitions which displayed direct-reaction characteristics. $J$ dependence was observed in $l=2\mathrm{} \mathrm{}\left(1d\right)\mathrm{}$ and $l=1\mathrm{} \mathrm{}\left(2p\right)\mathrm{} \mathrm{}(d,p)\mathrm{}$ transitions for $E_d=18.00\mathrm{}$ MeV. The spectroscopic factors obtained in this experimental study are compared with the predictions of current theoretical models which treat nuclei in the upper $s-d$ shell.

The ($p,n$) thresholds for the formation of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{P}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{Cl}$, and ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$ from targets of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$, respectively, have been measured relative to the ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}\mathrm{}(p,n)\mathrm{}{}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ threshold by detecting $\beta$ rays from these short-lived activities. Half-lives were determined by multiscaling techniques. The resulting ($p,n$) thresholds (in keV), half-lives (in msec) are as follows: ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ (15419±6, 442±5); ${}_{}{}^{28}{}_{}{}^{}\mathrm{P}$ (15 666±6, 266±4); ${}_{}{}^{32}{}_{}{}^{}\mathrm{Cl}$ (13 902±9 and 13 978±16, 281±8); ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$ (13 976±8, 336±4). The half-life of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ was measured as 2.054±0.009 sec.

Optical-model calculations have been made of the sensitivity of the ratio of ${\pi }^{\pm }$ absorption cross sections to the neutron-density distribution. Ratios accurate to a few tenths of 1% should be useful in determining neutron-density parameters.

The reactions ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}(\alpha ,t){}_{}{}^{91}{}_{}{}^{}\mathrm{Nb}$ and ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}(\alpha ,t){}_{}{}^{93}{}_{}{}^{}\mathrm{Tc}$ have been investigated with a 50-MeV $\alpha$-particle beam from the Berkeley 88-in. cyclotron. Comparisons are made with the results of (${}_{}{}^3{}_{}{}^{}\mathrm{He},d$) experiments on the same targets in order to locate high-spin ($l>\mathrm{}2\mathrm{}$) levels in ${}_{}{}^{91}{}_{}{}^{}\mathrm{Nb}$ and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Tc}$. The ${}_{}{}^{91}{}_{}{}^{}\mathrm{Nb}$(4.18 MeV) and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Tc}$(3.91 MeV) levels are probable $l=4\mathrm{} or 5$ levels, in contrast to the (${}_{}{}^3{}_{}{}^{}\mathrm{He},d$) results. A difference in $Q$ values for the reactions ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}(\alpha ,t){}_{}{}^{91}{}_{}{}^{}\mathrm{Nb}$ and ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}(\alpha ,t){}_{}{}^{92}{}_{}{}^{}\mathrm{Nb}$ of 680 ± 25 keV yields a $Q$ value for the reaction ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}(\alpha ,t){}_{}{}^{91}{}_{}{}^{}\mathrm{Nb}$ of -14.643 ± 0.027 MeV, which is not consistent with the presently accepted mass excess of -86.750 ± 0.06 MeV for ${}_{}{}^{91}{}_{}{}^{}\mathrm{Nb}$.

Excitation functions have been measured for $\gamma$-ray emmission following neutron inelastic scattering from the 2.186-, 2.319-, 2.748-, 2.748-, 3.077-, 3.310- and 3.84-MeV levels of ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ for neutrons in the energy range 2.85 to 5.97 MeV. The $\gamma$ rays were detected at 55° to the incident neutron beam using an anti-Compton spectrometer consisting of a NaI(T1) annulus enclosing a 45-${\mathrm{cm}}^3$ Ge(Li) detector. Multiple-scattering corrections were accounted for with the three-dimensional Monte Carlo code 05R. $\gamma$-ray angular distributions were calculated and used to deduce the total neutron inelastic scattering cross section from the cross section measured at 55°. These cross sections are in agreement with values calculated from Hauser-Feshbach theory corrected for level-width fluctuations and with previous measurements.

The ${\mathrm{Hg}}^{198}$ level scheme has been investigated from the ${\mathrm{Tl}}^{198}$ and ${\mathrm{Tl}}^{198m}$ ($\epsilon +{\beta }^{+}$) decays. A level scheme is proposed in which the following spins and parities have been determined by means of $\gamma$ and conversion-electron spectra and $\gamma -\gamma$ angular correlations: 1401.4 keV, $I^{\pi }=0^{+}$; 1612.7 keV, $I^{\pi }=2^{+}$; 1635.6 keV, $I^{\pi }=5^{-}$; 1832.8 keV, $I^{\pi }=2^{+}$; 1846.8 keV, $I^{\pi }=3^{+}$; 1858.9 keV, $I^{\pi }=2^{+}$; 1900.7 keV, $I^{\pi }=2^{+}$; 2360.6 keV, $I^{\pi }=3^{+}$. We have measured the isomeric cross-section ratio $\frac{\sigma {(\alpha ,3n)}^m}{\sigma {(\alpha ,3n)}^{\mathrm{g}.\mathrm{s}.\mathrm{}}}=5\mathrm{}\pm 1$ for $35 \mathrm{MeV}\le E_{\alpha }\le 42 \mathrm{MeV}$. Lifetimes of two negative-parity states have been determined: $\tau (1635.6\mathrm{} \mathrm{keV},5^{-})=89\mathrm{}\pm 15$ psec and $\tau (1683.4\mathrm{} \mathrm{keV},6^{-}{7}^{-})=10.7\mathrm{}\pm 0.5$ nsec which lead to $B(E2; 6^{-},7^{-}\to 5^{-})=0.17\mathrm{}\pm 0.02 {\left(e \mathrm{b}\right)}^2$; $B(E1; 5^{-}\to 4^{+})=(3.5\mathrm{}\pm 0.6)\times {10}^{-7\mathrm{}} e^{2}b$; $B(M2; 5^{-}\to 4^{+})=0.033\mathrm{}\pm 0.008 {{\mu }_N}^2\mathrm{b}$. Experimental data are well reproduced by calculations based on the hole-core coupling model using a pairing residual force between proton holes.