Cross sections and the first three moments of the $\gamma$-ray multiplicity distribution were measured for many transitions in a series of ${}_{}{}^{170-x}{}_{}{}^{}\mathrm{Yb}$ and ${}_{}{}^{166-x}{}_{}{}^{}\mathrm{Er}$ products from bombardments of ${}_{}{}^{158}{}_{}{}^{}\mathrm{Gd}$ with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at five energies corresponding to excitation in ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$ between 94 and 143 MeV. The average multiplicity for each $\mathrm{xn}$ channel increases with energy at first and then levels off at ∼ 21. For the $\alpha \mathrm{xn}$ channels saturation values between 16 and 20 are found. The excitation functions for ${}_{}{}^{166-x}{}_{}{}^{}\mathrm{Er}$ indicate that the isotopes with small $x$ are formed primarily by $2p(x+2\mathrm{})n$ evaporation and the ones with large $x$ by $\alpha \mathrm{xn}$ emission. A corresponding discontinuity in the average multiplicity vs $x$ observed. These features are absent in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ + ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$ reactions at the same ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$ excitation, but are present in the ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}({}_{}{}^4{}_{}{}^{}\mathrm{He}, xn)$ reactions at excitations from 63 to 92 MeV. The present results are clear indications of pre-equilibrium emission of neutrons and possibly of $\alpha$ particles, setting in at bombarding energies ∼ 10 MeV per nucleon.

NUCLEAR REACTIONS ${}_{}{}^{158}{}_{}{}^{}\mathrm{Gd}({}_{}{}^{12}{}_{}{}^{}\mathrm{C}, \mathrm{xn}\gamma ){}_{}{}^{170-x}{}_{}{}^{}\mathrm{Yb}$, $x=5-11\mathrm{}$, ${}_{}{}^{158}{}_{}{}^{}\mathrm{Gd}({}_{}{}^{12}{}_{}{}^{}\mathrm{C}, \alpha \mathrm{xn}\gamma ){}_{}{}^{166-x}{}_{}{}^{}\mathrm{Er}$, $x=4-10\mathrm{}$, $E=112.0, 124.7, 141.7, 152.7, 164.7$ MeV, measured $\sigma \mathrm{}\left(E\right)\mathrm{}$, $\gamma$-ray average multiplicity, variance, and skewness; ${}_{}{}^{158}{}_{}{}^{}\mathrm{Gd}({}_{}{}^{12}{}_{}{}^{}\mathrm{C}, 2\alpha \mathrm{xn}\gamma ){}_{}{}^{162-x}{}_{}{}^{}\mathrm{Dy}$, $x=4-7\mathrm{}$, $E=164.7\mathrm{}$ MeV, measured $\sigma$; deduced angular momentum removal by $\gamma$ rays and particles, $J$ distributions in evaporation residues, pre-equilibrium effects. Enriched target.

Neutron time-of-flight spectra and $\alpha$-particle spectra were obtained in coincidence with $\gamma$ rays characteristic of specific evaporation residues in the reactions 174.8 MeV ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ + ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$ and 152.0 MeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{158}{}_{}{}^{}\mathrm{Gd}$, producing ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$ at 134.2 and 132.0 MeV of excitation. The average multiplicity of $\gamma$ rays associated with such coincident events were also determined. The neutron spectra from the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ reactions are characteristic of equilibrium evaporation processes. They show a temperature $t\sim 2$ MeV, in agreement with a prediction from level-density parameters based on data at far lower excitation energy. The neutron spectra from the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reactions show a low-temperature equilibrium component (average $t\sim 1.8$ MeV) and a high-temperature ($t\sim 6$ MeV) pre-equilibrium component. The latter observation may be interpreted as evidence for the transient existence of a hot spot involving no more than 25 nucleons. The estimated number of pre-equilibrium neutrons emitted varies from 1.8 to 0.6 for the $8n$ to $10n$ products and from 1.2 to 0.25 for the $\alpha 6n$ to $\alpha 9n$ products. The fraction of ${}_{}{}^{166-x}{}_{}{}^{}\mathrm{Er}$ products formed by $2p(x+2\mathrm{})n$ rather than $\alpha \mathrm{xn}$ emission decreases with increasing $x$ for both the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reactions, and is roughly twice as large for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. The high-energy portions of the $\alpha$-particle spectra from (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $\alpha \mathrm{xn}$) for small $x$ exhibit a strong dependence on exit channel and on angle of emission, indicating clearly that these $\alpha$ particles are emitted from a nonequilibrated system. The angular correlations of the higher-energy $\alpha$ particles from (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $\alpha 7n$) to (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $\alpha 10n$) all have the same shape, suggesting that in these channels the $\alpha$ emission occurs first. The pre-equilibrium emission accounts for (16±7)% and (28±6)% of the total (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $\mathrm{xn}$) and (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $\alpha \mathrm{xn}$) cross sections, respectively. For these reactions the average multiplicities ${〈M〉}_{\mathrm{xn}}$ and ${〈M〉}_{\alpha \mathrm{xn}}$ from coincidences with neutrons and $\alpha$ particles of all energies saturate at ∼20.5 for $x\le 9 \mathrm{and} \le 8$, respectively, showing that the pre-equilibrium emission limits the angular momentum that can be imparted to the product nuclei prior to $\gamma$ decay. For (${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, $\alpha \mathrm{xn}$) evidence for such a limiting effect was found for $x\le 7$ and the $\alpha$-particle spectra show some hardening for $x\le 7$, but there is no evidence for pre-equilibirum emission in the (${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, $\mathrm{xn}$) reactions. The multiplicity from (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $\alpha 8n$) associated with $E_{\alpha }\ge 24$ MeV was found to be lower at forward $\alpha$-emission angles, apparently another manifestation of pre-equilibrium emission.

NUCLEAR REACTIONS ${}_{}{}^{158}{}_{}{}^{}\mathrm{Gd}({}_{}{}^{12}{}_{}{}^{}\mathrm{C}, \mathrm{xn}\gamma ){}_{}{}^{170-x}{}_{}{}^{}\mathrm{Yb}$, $x=7-11\mathrm{}$, ${}_{}{}^{158}{}_{}{}^{}\mathrm{Gd}({}_{}{}^{12}{}_{}{}^{}\mathrm{C}, \alpha \mathrm{xn}\gamma ){}_{}{}^{166-x}{}_{}{}^{}\mathrm{Er}$, $x=5-10\mathrm{}$, $E=152.0\mathrm{}$ MeV; ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}({}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}, \mathrm{xn}\gamma ){}_{}{}^{170-x}{}_{}{}^{}\mathrm{Yb}$, $x=7-10\mathrm{}$, ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}({}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}, \alpha \mathrm{xn}\gamma ){}_{}{}^{166-x}{}_{}{}^{}\mathrm{Er}$, $x=6-9\mathrm{}$, $E=174.8\mathrm{}$ MeV; measured $\sigma (E_n, {\theta }_n)$, $\sigma (E_{\alpha }, {\theta }_{\alpha })$, average $\gamma$-ray multiplicity; deduced temperatures, pre-equilibrium effects, $\mathrm{}(2p+2n)\mathrm{xn}$ fraction. Enriched targets.

From a study of the ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}({}_{}{}^6{}_{}{}^{}\mathrm{Li}, d)$ reaction at 32 MeV, angular distributions and $\alpha$-particle spectroscopic strengths have been extracted for states below 4.6-MeV excitation in ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$. The $\frac{5}{2^{+}}$ state at 0.35 MeV is populated largely via $L=0\mathrm{}$, and five states with $J^{\pi }$ from $\frac{1}{2^{+}}$ to $\frac{9}{2^{+}}$ largely via $L=2\mathrm{}$. These results are in reasonable agreement with predictions of SU(3) shell-model calculations and at the same time are suggestive of a simple weak-coupling picture. Observation of $L=0\mathrm{}$ for the transition to the 4.52-MeV level, previously assigned $\frac{3}{2^{+}}$ or $\frac{5}{2^{+}}$, allows a definite assignment of $J^{\pi }=\frac{5}{2^{+}}$.

NUCLEAR REACTIONS ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}({}_{}{}^6{}_{}{}^{}\mathrm{Li}, d)$, $E_{\mathrm{Li}}=32\mathrm{}$ MeV measured $\sigma \left(\theta \right)$; DWBA analysis, deduced $\alpha$-particle spectroscopic factors. Enriched target.

Correspondences are shown between semiclassical and quantum mechanical calculations that employ the same real potential. Comparisons are made to experimental scattering, complete fusion, and total reaction cross sections for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The separate roles of rainbow and absorptive effects are shown. Deductions of the nuclear potential from fits to data clearly depend on the adopted sequence of data fitting procedures and the freedom given at each stage to the parameters of the chosen potential. It is this sequence that plays a large role in the inference of weak vs intermediate vs strong surface absorption. The sequence we choose implies intermediate surface absorption for this case. Parameter adjustments are explored for data fits that employ the proximity potential.

NUCLEAR REACTIONS Classical, semiclassical, and quantum mechanical analysis for the system ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. Elastic scattering, fusing, and all reactive collisions are treated and related to classical turning points for each $l$ wave.

The trend of empirical interaction barriers and related parameters is explored for various heavy ion reaction systems for $100<\mathrm{}{Z}_1{Z}_2<1600\mathrm{}$. The empirical radius parameters from reaction cross sections differ significantly from those from elastic scattering quarter points for $Z_1{Z}_2<1000\mathrm{}$, but seem to approach one another for $Z_1{Z}_2>1000\mathrm{}$. This behavior is shown to be consistent with predominantly refractive scattering for low $Z_1{Z}_2$ and dominance for surface absorption for $Z_1{Z}_2>1000\mathrm{}$.

NUCLEAR REACTIONS Semiclassical analysis of elastic scattering and reaction cross sections of heavy ions; predominantly refraction for $Z_1{Z}_2<500\mathrm{}$ and strong absorption for $Z_1{Z}_2>1000\mathrm{}$.

A model is presented which is capable of calculating simultaneously the spectra of pions, nucleons, and light nuclei from the collision of relativistic heavy ions. It is based on the nuclear thermodynamics of Mekjian and Kapusta. Maximum use is made of the conservation laws for baryon number, charge, energy, momentum, and angular momentum. Single particle inclusive cross sections were calculated and compared with experiment for a wide range of beam energies and observed fragments. Except for some conflicting normalizations and high-energy pions good agreement is found. The density at which hadrons effectively cease to interact, which is the only parameter in the model, is determined to be 0.12 hadrons/${\mathrm{fm}}^3$.

NUCLEAR REACTIONS Relativistic heavy ions; firestreaks, hadronic thermal equilibrium; calculated differential cross sections of ${\pi }^{\pm }$, $p$, $d$, $t$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^4{}_{}{}^{}\mathrm{He}$; comparisons with experiment.

The reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^6{}_{}{}^{}\mathrm{Li}, d){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ has been studied in the 20-34 MeV incident energy range. Angular distributions have been taken at 28 MeV and 34 MeV incident ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ energies; the data have been analyzed in terms of Hauser-Feshbach and exact finite range distorted-wave Born-approximation theories. The extracted $\alpha$ spectroscopic strengths are compared with the predictions of SU(3) shell model.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^6{}_{}{}^{}\mathrm{Li}, d)$ $E=20-34\mathrm{}$ MeV; measured $\sigma (E, \theta )$; ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ levels deduced $S$. HF and EFR-DWBA analysis.

The ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ nucleus was studied measuring the electrofission yield and angular distributions of fission fragments, in the energy range of 5.5 to 28.3 MeV, using a new method of analysis. An $E2\mathrm{}$ isoscalar giant resonance was found in the photofission cross section of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. This resonance exhausts (71 ± 7)% of the energy-weighted sum rule and is located at 9.9 ± 0.2 MeV with a width of 6.8 ± 0.4 MeV. The position of this resonance is in reasonable agreement with the Bohr and Mottelson prediction ($58A^{-\frac{1}{3}}$ MeV). The width of 6.8 ± 0.4 MeV is compatible with a possible triple splitting of the resonance. From the angular distributions of photofission fragments and yield measurements of multipoles other than $E1\mathrm{}$, evidence of an $M1\mathrm{}$ mixture in the energy region 6-7 MeV was found.

NUCLEAR REACTIONS, FISSION Electrofission of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ ($e, e\text{'}f$), $E_0=5.5\mathrm{} \mathrm{to} 28.3$ MeV, measured electrofission yield and angular distributions of fission fragments. Deduced $E2\mathrm{}$ cross section and $E2\mathrm{}$ isoscalar giant resonance parameters.

The fourth-order iterative diagrams involving $N\Delta$ and $\Delta \Delta$ intermediate states and including $\pi$ as well as $\rho$ exchange are calculated in momentum space without any approximation. It turns out that, due to retardation effects in the propagators, these contributions are by a factor of 3 smaller than former models using twice-iterated transition potentials with simple propagators of pion (and $\rho$) range. This fact allows the use of much shorter-range cutoffs at the $N\Delta$ vertices than before. $\mathrm{NN}$ scattering phase shifts are calculated using these diagrams together with a suitably modified one-boson exchange potential, likewise derived from noncovariant perturbation theory. The effect of the $N\Delta \rho$ vertex is different in various partial waves; its decisive role in getting a consistent description, especially of the important ${}_{}{}^3{}_{}{}^{}P$ phases, is demonstrated. It is shown that the static limit (necessarily used by other groups working in $r$ space) is not a good approximation and, moreover, its effect cannot be mocked up by a mere change of parameters.

NUCLEAR REACTIONS Nucleon-nucleon interaction, $\mathrm{NN}\to N\Delta$ and $\mathrm{NN}\to \Delta \Delta$ transition potentials with $\pi$ and $\rho$ exchange, noncovariant perturbation theory.

Reaction mechanisms for $\mathrm{pd}\to \mathrm{nd}{\pi }^{+}$ are examined at energies in the $\Delta$ resonance region. A model based on single and double scattering amplitudes with $\pi$ production at any one of the vertices provides a reasonable fit to the data.

NUCLEAR REACTIONS ($p, {\pi }^{+}n$), ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ target; calculated differential cross sections at $E_p=585\mathrm{}$ MeV.

Because of the effects of the medium on the pion dispersion relation, the lepton spectrum in the inclusive reaction $\overline{\nu }+\mathrm{nucleus}\to l^{+}+\mathrm{anything}$ will show sharp peaks due to production of a pion into the nuclear matter in the interior of the nucleus. For the case of a 420 MeV incident $\overline{\nu }$, detailed calculations show that these peaks will be far above expected backgrounds and that their observation can give a direct, point by point determination of the pion dispersion relation in nuclear matter.

NUCLEAR REACTIONS Neutrino reactions on nuclei to determine pion dispersion relation.

We estimate the Coulomb energy component of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^3{}_{}{}^{}\mathrm{H}$ binding energy difference, using the latest elastic electron scattering form factor data, to be 639±19 keV, in agreement with previous estimates. We estimate the Coulomb energy of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ to be 757±23 keV. We discuss the Coulomb energy contribution to the $\Lambda$ separation energy difference $B_{\Lambda }\left({}_{\Lambda }{}^4{}_{}{}^{}\mathrm{He}\right)-B_{\Lambda }\left({}_{\Lambda }{}^4{}_{}{}^{}\mathrm{H}\right)$.

NUCLEAR STRUCTURE Coulomb energy, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^3{}_{}{}^{}\mathrm{H}$, ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{\Lambda }{}^4{}_{}{}^{}\mathrm{He}$, $\Lambda$-separation energy.

Modifications of the Chew-Low theory caused by the inclusion of $\rho$-nucleon intermediate states are examined. Although this effect changes the form factors necessary to reproduce the (3, 3) resonance, no significant change in the resulting phase shifts is obtained. The use of $\rho$-nucleon intermediate states does not eleiminate the "ghost state" pole in those spin-isospin channels for which the driving term is repulsive.

NUCLEAR REACTIONS Scattering theory, Low equation, $\pi$-nucleon scattering.

We show that the peripheral part of the elastic scattering impulse approximation can be expressed entirely in terms of on-shell information. The impulse approximation is given in terms of an integral over the onshell elementary amplitude. We find the range of energies required in that amplitude for the peripheral part and discuss the closure approximation to this integral.

NUCLEAR REACTIONS Scattering theory, low density limit of the impulse approximation. Application to $\pi$-nucleus scattering and $K$-mesonic atoms.

A momentum space method for hadronic atoms is developed to incorporate relativistic, nonlocal, complex hadron-nucleus interactions. The logarithmic singularity due to the Coulomb interaction has been treated by Lande's subtraction technique. Vacuum polarization, and both nuclear and pion finite-size effects have been included in this momentum space method. Precision eigenvalues and eigenfunctions for the Schrödinger, relativistic Schrödinger, Klein-Gordon (of various types), and Dirac equations have been calculated using a rapid and convenient inverse iteration method. Reliability of this novel approach is confirmed by comparing with parallel coordinate space methods. Several illustrative applications are made to simple pionic, and kaonic cases to demonstrate possible applications. For example, it is found that: (1) to extract the pion size from pionic atom data, energy shifts must be measured to an accuracy of better than 50 eV; (2) to determine the form of Klein-Gordon equations appropriate for kaonic atoms, one needs a precision of better than 20 eV; (3) the finite-range of the $\pi -N$ interaction plays a non-negligible role and, therefore, should be carefully included in the pion-nucleus interaction. More extensive applications of these methods are suggested.

NUCLEAR STRUCTURE Hadronic atoms, momentum space formulation, and its applications.

The Panofsky ratio and photopion production cross section at threshold on ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ are investigated in a softpion approach to the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$→${}_{}{}^3{}_{}{}^{}\mathrm{H}$ weak axial-vector form factor. Results are compared with data on $\beta$ decay and electron magnetic scattering, as well as with calculations based on "exact" $A=3\mathrm{}$ wave functions previously obtained by solving the Faddeev equations in the coordinate representation.

NUCLEAR REACTIONS Calculations on ${\pi }^{-}\left(\mathrm{stopped}\right)+{}_{}{}^3{}_{}{}^{}\mathrm{He}\to \gamma +{}_{}{}^3{}_{}{}^{}\mathrm{H}$, ${\pi }^{-}\left(\mathrm{stopped}\right)+{}_{}{}^3{}_{}{}^{}\mathrm{He}\to {\pi }^0+{}_{}{}^3{}_{}{}^{}\mathrm{H}$, $\gamma \left(\mathrm{threshold}\right)+{}_{}{}^3{}_{}{}^{}\mathrm{He}\to {\pi }^{+}+{}_{}{}^3{}_{}{}^{}\mathrm{H}$. (${}_{}{}^3{}_{}{}^{}\mathrm{He}$→${}_{}{}^3{}_{}{}^{}\mathrm{H}$) weak axial-vector form factor. Model three-nucleon wave functions.

High-energy heavy-ion reaction data on pion production near ${\theta }_{\mathrm{lab}}=0\mathrm{}° \mathrm{and} 180°$ are analyzed. The result strongly suggests that the forward (backward) pions are due to materialization of the kinetic energy of the "effective projectiles" ("effective targets") in peripheral nucleus-nucleus collisions. A statistical interpretation for the observed energy distributions is discussed.

NUCLEAR REACTIONS Proton and HI projectiles on various targets (H to Pb) at $E=1.05-7.52\mathrm{}$ GeV/nucl.; analyzed single-pion inclusive spectra at forward and backward directions (${\theta }_{\mathrm{lab}}\approx 0° \mathrm{and} 180°$); discussed cumulative effect and statistical interpretation in HI reactions.

He ions emitted in the interaction of 70-MeV pions with carbon, aluminum, nickel, silver, and gold were measured directly at $\theta =90\mathrm{}°$. Cross sections and energy spectra are presented. Calculations of intranuclear cascades followed by evaporation reproduced the experimental data reasonably well. The results of the calculations imply that: (1) pion absorption in flight plays a major role in reactions in which $\alpha$ particles are emitted; and (2) one-"$\alpha$"-removal lines, observed in deexcitation $\gamma$-ray experiments, do not imply large probability for real $\alpha$ emission. The ${\pi }^{-}$ to ${\pi }^{+}$ ratio of cross sections was found to be about 1.4.

NUCLEAR REACTIONS C, Al, Ni, Ag, Au (${\pi }^{-}, \alpha +\mathrm{anything}$), $E_{\pi }=70\mathrm{}$ MeV; measured He energy spectra; $\frac{d\sigma }{d\Omega }\left(90\mathrm{}°\right)$. Natural targets; evaporation analysis.

The half-life of ${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$ was measured by $\alpha$ counting with an intermediate geometry proportional counter, using oxidation-reduction titration of the plutonium to measure its mass. The specific activity is (5.033 ± 0.004) × ${10}^{11}$ $\alpha$ disintegrations per minute per gram; the half-life is 6569 ± 6 yr (one standard deviation error).

RADIO ACTIVITY ${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$ half-life, specific activity; measured: $\alpha$ activity by intermediate geometry $\alpha$ counter; plutonium concentration, redox titration.

The higher energy portion of the inner bremsstrahlung spectrum accompanying the allowed orbital electron capture transition in ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ to the ground state of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ was measured with a single channel NaI(Tl) scintillation spectrometer. Correction for the pileup spectrum due to the 478 keV nuclear $\gamma$ rays arising from the deexcitation of the first excited state in ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ was performed by numerical integration. The measured pulse-height distribution of the inner bremsstrahlung photons was corrected for detector response following the procedures of Liden and Starfelt and Palmer and Laslett. For energies higher than 560 keV the number of $1S+2S$ bremsstrahlung photons emitted per ground state EC decay of ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ was determined to be (6.31 ± 0.38) × ${10}^{-5\mathrm{}}$. Corresponding theoretical values are 6.46 × ${10}^{-5\mathrm{}}$, deduced from Martin - Glauber theory, and 6.45 × ${10}^{-5\mathrm{}}$, deduced from the improved calculations of Intemann. The present result is in good agreement with the theoretical predictions. The decay energy of ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ was determined to be 857 ± 14 in agreement with the accepted atomic mass difference.

RADIOACTIVITY ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$; measured inner bremsstrahlung, $\gamma$; deduced $I_{\mathrm{IB}}$, $Q$. NaI(Tl) detector, numerical integration method.