The $\frac{E2\mathrm{}}{M1\mathrm{}}$ multipole mixing ratios $\delta \left(\gamma \right)$ of $\gamma$ transitions in even-even osmium and platinum isotopes have been measured in order to test the predictions of the pairing-plus-quadrupole theory of Kumar and Baranger. The mixing ratios $\delta \left(\gamma \right)$ were determined from directional-correlation measurements on $\gamma$ transitions in ${}_{}{}^{186,188,190}{}_{}{}^{}\mathrm{Os}$ (populated in the decay of ${}_{}{}^{186,188,190}{}_{}{}^{}\mathrm{Ir}$ and in ${}_{}{}^{194,196}{}_{}{}^{}\mathrm{Pt}$ (populated in the decay of ${}_{}{}^{194,196}{}_{}{}^{}\mathrm{Au}$). The radioactive iridium isotopes were produced by $\mathrm{Re}(\alpha ,xn)$ reactions, and the gold isotopes were produced by $\mathrm{Pt}\mathrm{}(d,xn)\mathrm{}$ reactions. The equipment employed for the $\gamma -\gamma$ directional-correlation measurements consisted of two coaxial 30-cc Ge(Li) detectors and appropriate electronic equipment for high-resolution pulse-height analysis and timing analysis. The observed directional correlations were analyzed in terms of the appropriate $\frac{E2\mathrm{}}{M1\mathrm{}}$ mixing ratios, which are defined explicitly. The following results were obtained (predictions of the Kumar-Baranger theory are listed in square brackets): $\delta ({}_{}{}^{186}{}_{}{}^{}\mathrm{Os}, 630 \mathrm{keV})=-\left({10}_{-4\mathrm{}}^{+15\mathrm{}}\right)[-14.7\mathrm{}]\mathrm{}$, $\delta ({}_{}{}^{186}{}_{}{}^{}\mathrm{Os}, 773 \mathrm{keV})=-\left({13}_{-6\mathrm{}}^{+9\mathrm{}}\right)[-13.5\mathrm{}]\mathrm{}$, $\delta ({}_{}{}^{188}{}_{}{}^{}\mathrm{Os}, 478 \mathrm{keV})=-12.3\mathrm{}\pm 2.8 \mathrm{}[-9.5\mathrm{}]\mathrm{}$, $\delta ({}_{}{}^{188}{}_{}{}^{}\mathrm{Os}, 635 \mathrm{keV})=-6.9\mathrm{}\pm 3.2 \mathrm{}[-10.5\mathrm{}]\mathrm{}$, $\delta ({}_{}{}^{190}{}_{}{}^{}\mathrm{Os}, 371 \mathrm{keV})=-8.5\mathrm{}\pm 1.0 \mathrm{}[-7.6\mathrm{}]\mathrm{}$, $\delta ({}_{}{}^{190}{}_{}{}^{}\mathrm{Os}, 569 \mathrm{keV})=-9.0\mathrm{}\pm 1.5 \mathrm{}[-9.9\mathrm{}]\mathrm{}$, $\delta ({}_{}{}^{194}{}_{}{}^{}\mathrm{Pt}, 293 \mathrm{keV})=+14.3\mathrm{}\pm 2.1 \mathrm{}[+19.9\mathrm{}]\mathrm{}$, $\delta ({}_{}{}^{196}{}_{}{}^{}\mathrm{Pt}, 333 \mathrm{keV})=-5.7\mathrm{}\pm 0.3 \mathrm{}[-101.4\mathrm{}]\mathrm{}$. Except for the 333-keV transition in ${}_{}{}^{196}{}_{}{}^{}\mathrm{Pt}$ the agreement of the experimental mixing ratios with the values and signs predicted by the Kumar-Baranger model is excellent.

An analysis of the $\beta$ spectrum of ${\mathrm{Mo}}^{99}$ taking into account the correct shape of the outer $\beta$ group revealed $\beta$ groups with end points 1214 ± 1 (84%), 840 ± 5 (2%), 450 ± 10 (14%) keV. The shape of the outer $\beta$ group (${\mathrm{½}}^{+}$ → ${\mathrm{½}}^{-}$) feeding the 142-keV level in ${\mathrm{Tc}}^{99}$ is expected to be statistical, obeying the $\xi$ approximation. The measured shape-factor coefficient $a$ is - 0.01 ± 0.007. On the basis of shell-model matrix elements, the conserved-vector-current prediction for A gave a positive value for $a$, whatever the value of ${\Lambda }_0$. Treating both $\Lambda$ and ${\Lambda }_0$ as free parameters, a fit to the experimental shape gave $3.4<~\Lambda <~5$ and $2.3<~{\Lambda }_0<~3.7$. The shape of the inner group (840 keV) was found to be consistent with first-forbidden nonunique character, and within experimental accuracy it was consistent with the shell-model prediction, even though the 514-keV (${\frac{3}{2}}^{-}$) level fed by this $\beta$ group is considered as arising from the weak coupling of a $p_{\frac{1}{2}}$ proton to the $2^{+}$ first excited state of the core. But the large $log\mathrm{ft}$ value of this transition may perhaps be explained by a detailed "microscopic" picture of the core.

A new very weak $\beta$ group 414 ± 10 (0.9%) keV is revealed in addition to the three $\beta$ groups with end points 1035 ± 2 (92%), 789 (1.1%), and 693 ± 3 (6.0%). The 414-keV $\beta$ group feeds the 621-keV level of ${\mathrm{Cd}}^{111}$ introduced by Sastry, Lakshminarayana, and Jnanananda. The large shape deviation (17%) reported by Langer et al. for the 693-keV $\beta$ group indicated a breakdown of the $\xi$ approximation for this group, whereas correlation experiments and theoretical predictions indicated statistical shape. The present measurement $C\left(W\right)=k[1-(0.01\mathrm{}\pm 0.06\left)W\right]$ confirms the latter conclusions and is in quantitative agreement with the shell-model predictions of Delabaye, Deutsch, and Lipnik. The characteristics of ${\mathrm{½}}^{-}$ → ${\mathrm{½}}^{+}$ and ${\mathrm{½}}^{-}$ → ${\frac{3}{2}}^{+}$ transitions are just similar to those of ${\mathrm{Mo}}^{99}$ and a theoretical fit of the outer $\beta$ group of ${\mathrm{Ag}}^{111}$ yields $3.2<~\Lambda <~3.3$ and $1.2<~{\Lambda }_0<~1.4$.

Irradiation of enriched ${}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}$ with 14.7-MeV neutrons was found to produce a new radioactive nuclide which was assigned to ${}_{}{}^{180}{}_{}{}^{}\mathrm{Lu}$. The following radiation characteristics were observed to belong to the decay of ${}_{}{}^{180}{}_{}{}^{}\mathrm{Lu}$: half-life 5.8±0.2 min; $\gamma$-ray energies 93.3±0.8, 215.3±0.8, 316.8±0.8, 408.4±0.8, 464.4±0.8, 1065.2±1.5, 1106.8±0.8, 1197±1, 1199.5±0.8, 1298.8±0.8, 1315.0±1.0, 1433.6±1.0, 1514.3±0.8, and 1873.9±2.0 keV; and a $\beta$ ray of 1.45±0.10 MeV. A tentative decay scheme is presented and discussed.

The composite ($K$-orbital shakeoff plus nuclear) electron spectrum shape in coincidence with $K$ x rays in the pure $\beta$ emitter ${\mathrm{Pr}}^{143}$ ($E_0=930\mathrm{}$ keV) was measured with the Argonne magnetic-lens spectrometer and a NaI scintillation x-ray spectrometer. It yields an ordinary Kurie plot nearly linear from $E_{max}=888\mathrm{}\pm 5$ keV [930 keV — ($K$ binding energy)] to ∼160 keV, below which the contribution from the $K$ shakeoff spectrum appears as a sharply rising component down to <30 keV. This composite coincidence spectrum agrees fairly well with the recent relativistic shakeoff theory of Stephas and Crasemann, but only if their formulation for the square of the atomic matrix element is multiplied by a factor of $\frac{W}{p}$. Significant differences of both component shapes with this modified theory remain. Comparison of the measured shape to that calculated from the formulation of Feinberg for direct collision indicates that this process contributes negligibly to the decay. The ratio of the higher-energy Kurie component (mainly the nuclear $\beta$ component) of the composite spectrum to the singles intensity gives a total $K$-ionization probability $P_K=(2.95\mathrm{}\pm 0.3)\times {10}^{-4\mathrm{}}$; relativistic self-consistent-field wave-function overlap integrals give 3.0×${10}^{-4\mathrm{}}$.

Low-lying states in ${}_{}{}^{92}{}_{}{}^{}\mathrm{Nb}$ have been studied using the ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}(p,n\gamma ){}_{}{}^{92}{}_{}{}^{}\mathrm{Nb}$ reaction at $E_p=6.3\mathrm{}$ MeV. A $\mathrm{Ge}\left(\mathrm{Li}\right)\mathrm{} \gamma$ spectrum was measured in coincidence with neutrons to identify low-lying states and their $\gamma$ transitions. The mean lifetime of the 357-keV state was measured as $\tau =2.73\mathrm{}\pm 0.09$ nsec by a neutron-$\gamma$ delayed-coincidence technique. The mean lifetime of the 227-keV $2^{-}$ state obtained from a $\gamma -\gamma$ delayed-coincidence measurement is $\tau =6.2\mathrm{}\pm 0.7$ μsec. An upper limit of $\tau <~0.8$ nsec was measured for the mean lifetime of the 501-keV state. These lifetime results and observed $\gamma$ transitions established for the predicted $[\pi ,{\frac{9}{2}}^{+}]\left[\nu \right(2\mathrm{}{d}_{\frac{5}{2}}\left)\right]J^{+}$ configuration the level sequence $7^{+}$, $2^{+}$, $3^{+}$, $5^{+}$, $4^{+}$, $6^{+}$. A $B\left(E2\mathrm{}\right)=50.9\mathrm{} e^2 {\mathrm{F}}^4$ was deduced for the $5^{+}$ →$7^{+}$ (357→0 keV) transition from the lifetime of the 357-keV state; effective $E2\mathrm{}$ charges for the mass-90 region are compared. The lifetime of the $2^{-}$ state implies an $E1\mathrm{}$ hindrance of ${10}^7$ for the $2^{-}\to 2^{+}(227\mathrm{}\to 135 \mathrm{keV}) \gamma$ transition relative to single-particle estimates.

The energy spectra of neutrons from the $\alpha$-particle bombardment of deuterium at 38.8 MeV have been measured at lab angles of 15, 18, 21, 24, 30, 45, and 54°. Prominent features of the spectra are explainable on simple kinematic bases. The shapes of the energy spectra and the cross-section values are consistent with the calculations of Shanley and Nakamura but seem to be inconsistent with proton spectra from the same reaction as measured by Nagatani, Tombrello, and Bromley.

The $\gamma$ rays emitted following the decay of 21.8-min ${\mathrm{Gd}}^{145g}$ have been studied using Ge(Li) and NaI(Tl) detectors in a variety of singles, anticoincidence, pair-coincidence, and two-dimensional ("megachannel") coincidence experiments. Of the $38 \gamma$ rays attributed to this decay, 27 (accounting for >97% of the intensity) have been placed in a consistent decay scheme that includes 20 states in ${\mathrm{Eu}}^{145}$. All of the single-proton states between $Z=50\mathrm{} \mathrm{and} 82$ are seen (including the $h_{\frac{11}{2}}$ state populated directly by the decay of ${\mathrm{Gd}}^{145m}$), and the associated $\beta$ and $\gamma$ transitions are accounted for quite well using simple shell-model arguments. In addition, we propose an explanation for the abrupt change in decay properties of the $N=81\mathrm{}$ isotones that occurs at ${\mathrm{Gd}}^{145g}$, viz., the lack of observable population directly to the ${\mathrm{Eu}}^{145}$ ground state but 72.6% of its decay going to states at 1757.8 and 1880.6 keV. With a ${\left(\nu s_{\frac{1}{2}}\right)}^{-1\mathrm{}}$ ground state for ${\mathrm{Gd}}^{145}$, these "fast" $\beta$ transitions can be represented as ${\left(\pi h_{\frac{11}{2}}\right)}^{2n}{\left(\nu s_{\frac{1}{2}}\right)}^{-1\mathrm{}}\to {\left(\pi h_{\frac{11}{2}}\right)}^{2n-1}\left(\nu h_{\frac{9}{2}}\right){\left(\nu s_{\frac{1}{2}}\right)}^{-1\mathrm{}},$ making the final states another example of three-quasiparticle states being populated by the $\frac{{\beta }^{+}}{\epsilon }$ decay of nuclei below $N=82\mathrm{}$.

The single-neutron-hole states of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$ have been studied by means of the ($p,{}_{}{}^3{}_{}{}^{}\mathrm{He}$) and ($d,\alpha$) reactions on ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ at 40 and 20 MeV, respectively. Angular distributions were obtained for five of the six well-known neutron-hole states. The sixth state, the ${\left(1\mathrm{}{h}_{\frac{9}{2}}\right)}^{-1\mathrm{}}$ level at 3.43 MeV, was not adequately separated from a group of unresolved, strongly excited states between 3.5- and 7.5-MeV excitation energy in ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$. The data were compared with microscopic- and cluster-model two-nucleon-transfer calculations in the context of the distorted-wave Born approximation. Good agreement was found with theoretical predictions of the shapes and relative magnitudes of the angular distributions for the ($d,\alpha$) reaction. However, it was necessary to introduce a radial lower cutoff at 8.3 F to reproduce the shape of the ($p,{}_{}{}^3{}_{}{}^{}\mathrm{He}$) angular distributions. The experimental absolute normalization constants were computed and compared with theoretical predictions and with a previous experimental determination. The sensitivity of these normalization constants to various parameters of the theory was investigated.

The energy levels and transitions of ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ have been examined by high-resolution measurements of the $\gamma$ rays from the ($n,n^{\prime }\gamma$) reaction for incident neutrons between the energies of 0.2 and 2.2 MeV. The level scheme, up to an excitation of 1308 keV, is compared with a recent neutron time-of-flight study, and several new levels are proposed. Differential $\gamma$-ray production cross sections at 95° are given and spin and parity assignments for levels in this nucleus are discussed.

A NaI-Ge(Li) detector arrangement has been used to measure $\gamma -\gamma$ directional correlations in ${}_{}{}^{154}{}_{}{}^{}\mathrm{Gd}$ from the decay of ${}_{}{}^{154}{}_{}{}^{}\mathrm{Eu}$. From the NaI detector, gates were selected to span the 123-keV $2^{+}\to 0^{+}$, and 248-keV $4^{+}\to 2^{+}$ transition, and an equivalent region of the Compton distribution at 320 keV to obtain the background contribution to each gate. These gates opened 20488 channels of the memory of a 4096-channel analyzer for storage of data at 90, 135, and 180° from the Ge(Li) detector. The well-known 1274-123-keV and 873-123-keV correlations were used to obtain attenuation and Ge(Li) solid-angle corrections for cascades that involve the 123-keV $2^{+}$ state. The following correlations (in keV) were measured, with the $A_2$ and $A_4$ coefficients, respectively, in parentheses: 692-123, $2_{\beta }^{+}\to 2_g^{+}\to 0^{+}(-0.145\mathrm{}\pm 0.022,0.311\pm 0.040)$; 1005-123, $3_{\gamma }^{+}\to 2_g^{+}\to 0^{+}(-0.239\mathrm{}\pm 0.018$, -0.073 ± 0.026); 1494-123, $3^{-}\to 2_g^{+}\to 0^{+}(-0.075\mathrm{}\pm 0.029,-0.022\pm 0.044)$; 1597-123, $2^{-}\to 2_g^{+}\to 0^{+}(0.196\mathrm{}\pm 0.013$, -0.017 ± 0.021); 757-248, $3_{\gamma }^{+}\to 4_g^{+}\to 2_g^{+}(0.161\mathrm{}\pm 0.004$, -0.174 ± 0.006), 677-248, $4_{\beta }^{+}\to 4_g^{+}\to 2_g^{+}(-0.168\mathrm{}\pm 0.020,0.178\pm 0.029)$, 444-248, $2_{\beta }^{+}\to 4_g^{+}\to 0^{+}(0.196\mathrm{}\pm 0.009,0.095\pm 0.011)$; 625-248, $2_{\gamma }^{+}\to 4_g^{+}\to 2^{+}(0.187\mathrm{}\pm 0.014,0.108\pm 0.019)$; 893-248, $4_{\gamma }^{+}\to 4_g^{{}^{+}}\to 2^{+}(-0.037\mathrm{}\pm 0.010,0.160\pm 0.013)$; 881-248, $3^{-}\to 4_g^{+}\to 2^{+}(-0.132\mathrm{}\pm 0.058,-0.059\pm 0.086)$; 1188-248, $4^{-}\to 4_g^{+}\to 2^{+}(0.224\mathrm{}\pm 0.028,-0.010\pm 0.041)$; and 1246-248, $3^{-}\to 4_g^{+}\to 2^{+}(-0.151\mathrm{}\pm 0.007,0.010\pm 0.008)$. The following $M1\mathrm{}$ admixtures (in keV) were found in the transition from the $\beta$ and $\gamma$ bands: 692, $2_{\beta }^{+}\to 2_g^{+}\left({99.2}_{-0.7\mathrm{}}^{+0.3\mathrm{}}E2\right)$; 677, $4_{\beta }^{+}\to 4_g^{+}(>\mathrm{}80\%E2\mathrm{} \mathrm{for} 2\sigma \mathrm{limits})$; 1005, $3_{\gamma }^{+}\to 2_g^{+}\left({99.78}_{-0.23\mathrm{}}^{+0.20\mathrm{}}E2\right)$; 757, $3_{\gamma }^{+}\to 4_g(97.0\mathrm{}\pm 0.3\%E2)$; and 893, $4_{\gamma }^{+}\to 4_g^{+}(95.2\mathrm{}\pm 0.8\%E2)$. The transitions from the odd-parity states studied to the even-parity ground-state band are all 99.9 ± 0.1% $E1\mathrm{}$.

The effect of blocking, for odd systems, is included in the gap equations of the nuclear pairing theory for a general two-body interaction. These equations are applied to calculate the one-quasiparticle low-energy spectra, the neutron separation energies, and the "odd-even mass differences" for the Sn isotopes. The apparent inflation of the effective pairing strengths in calculations in which the blocking effect is ignored is pointed out.

Fission cross sections for the systems ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$ + ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{175}{}_{}{}^{}\mathrm{Lu}$ + ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{174}{}_{}{}^{}\mathrm{Y}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{182}{}_{}{}^{}\mathrm{W}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ + ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, and ${}_{}{}^{159}{}_{}{}^{}\mathrm{Tb}$ + ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ have been measured for heavy-ion bombarding energies up to 10.4 MeV per nucleon. The experimental technique consisted of counting coincident fission-fragment pairs with two gold-surface-barrier silicon-diode detectors. For the above systems, fission takes place only in reactions in which a compound nucleus is formed between the incident projectile and the target nucleus. Values of the compound-nucleus cross sections for these reactions are estimated from other data in order to account for surface reactions which occur in heavy-ion bombardment. The difference between the cross section for compoundnucleus formation and that for fission is assumed to be equal to the cross section for neutron-evaporation products. The ratio of the fission cross section to that for neutron evaporation is then taken to be equal to $〈\frac{{\Gamma }_f}{{\Gamma }_n}〉$, the ratio of the level widths for the two competing processes averaged over the various reaction channels. A theoretical fit to the $〈\frac{{\Gamma }_f}{{\Gamma }_n}〉$ values is obtained for the low-energy region of the excitation function, where first-chance fission is highly probable. We find the ratio of the level-density parameter for fission to that for neutron emission to be 1.2 ± 0.1, and values for the fission barrier to be in agreement with those predicted by Myers and Swiatecki.

The ($d,p$) reaction on ${\mathrm{Ru}}^{102}$ and ${\mathrm{Ru}}^{104}$ has been studied at an incident deuteron energy of 14 MeV. Proton spectra were recorded in a broad-range magnetic spectrograph. Transferred $l$ values and spectroscopic factors were obtained by comparing the measured angular distributions with distorted-wave Born-approximation predictions. The low-lying levels of ${\mathrm{Ru}}^{103}$ are in good agreement with the results of a recent ($d,t$) study; information on higher levels of ${\mathrm{Ru}}^{103}$ and on all levels in ${\mathrm{Ru}}^{105}$ is new. There is good correspondence between strongly excited levels in the two isotopes, although there is evidence of a higher level density in ${\mathrm{Ru}}^{105}$. The summed spectroscopic factors give information on the extent of filling of the neutron orbitals in the targets, and these results are in reasonable agreement with results from the ($d,t$) reaction and for other nuclei in this region.

The lifetimes of a number of ground-band states in ${}_{}{}^{148,150,152}{}_{}{}^{}\mathrm{Sm}$ have been measured by the recoil-distance Doppler-shift method following Coulomb excitation by backscattered ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ projectiles. The measured $B\left(E2\mathrm{}\right)\mathrm{}$ values for ${}_{}{}^{152}{}_{}{}^{}\mathrm{Sm}$ are larger than the rigid-rotor values; in terms of the mixing or stretching parameter $\alpha$ the present experiments yield $\alpha =(+2.2\mathrm{}\pm 0.7)\times {10}^{-3\mathrm{}}$. For ${}_{}{}^{148,150}{}_{}{}^{}\mathrm{Sm}$ the measured $B\left(E2\mathrm{}\right)\mathrm{}$ values are near those expected for vibrational nuclei.

The ${}_{}{}^{210}{}_{}{}^{}\mathrm{Pb}(p,d){}_{}{}^{209}{}_{}{}^{}\mathrm{Pb}$ reaction has been studied at an energy of 20.6 MeV in the angular range 13-17°. The objectives of the work were twofold. First, the fragmentation of the two-particle-one-hole ${{\nu }_{0^{+}}}^2{{\nu }_{{\mathrm{nl}}_j}}^{-1\mathrm{}}$ strength up to an excitation in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Pb}$ of 5.3 MeV was investigated and compared with the corresponding ${{\nu }_{{\mathrm{nl}}_j}}^{-1\mathrm{}}$ strength in ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$ as reported in a recent study of the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}\mathrm{}(p,d)\mathrm{}$ reaction at 20 and 22 MeV. Second, the microscopic structure of the valence neutrons ${{\nu }_{0^{+}}}^2$ in the ground state of ${}_{}{}^{210}{}_{}{}^{}\mathrm{Pb}$ was investigated by measuring the spectroscopic factors for pickup to the six low-lying neutron single-particle states in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Pb}$.

An off-shell $t$ matrix is developed for the boundary-condition model in the general case of coupled partial waves. This development is facilitated by the use of a method for solving the Lippmann-Schwinger equation directly for potentials of the square-well type. The $t$ matrix obtained is shown to be unique under some rather mild assumptions as to analyticity and asymptotic behavior. An integral equation of the Lippmann-Schwinger type is obtained for the $t$ matrix in the more realistic problem of boundary condition plus external potential.

The production of internal bremsstrahlung accompanying $\beta$ decay from radioactive nuclei of ${\mathrm{Tl}}^{204}$, ${\mathrm{Pm}}^{147}$, and ${\mathrm{Ca}}^{45}$ has been investigated. The $\beta$-active source is fixed to the source holder of an experimental chamber with a good collimating arrangement. The internal bremsstrahlung is detected by a scintillation counter of good resolution and known efficiency, and a differential spectrum is obtained using a single-channel pulse analyzer. After making all necessary corrections, the probability of internal bremsstrahlung /$m{c}^2$ per $\beta$ disintegration is obtained. The experimental probability is compared with the theoretical probabilities calculated from the theories of Knipp, Uhlenbeck, and Bloch; Nilsson; and Lewis and Ford. Discrepancies have been observed between experimental and theoretical results, especially in the case of ${\mathrm{Ca}}^{45}$, which has not been investigated previously. The experimental results show a distinct deviation from theoretical predictions.

The absolute energy spectrum of prompt photons emitted from the fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ by thermal neutrons was measured in the range from 0.01 to 10 MeV by using single-crystal, Compton, and pair NaI(Tl) scintillation spectrometers. Each was operated in ≤69-nsec coincidence with a fission chamber exposed to thermal neutrons from a reactor. The pulse-height response functions of the spectrometers were constructed in detail by exposing the spectrometers to radioactive sources of known disintegration rates. These data were used to "unfold" the measured pulse-height spectra to give the absolute differential energy spectrum and its random uncertainties. A careful analysis of systematic uncertainties was also performed. The average number of photons per fission is 8.13 ± 0.35 and the average photon energy release per fission is 7.25 ± 0.26 MeV, both over the energy region from 10 keV to 10.5 MeV. The results obtained here are in approximate agreement with the recent measurement by Verbinski and Sund in the energy region above 140 keV. From 1.5 to 4 MeV the calculation of Zommer, Savel'er, and Prokofiev gives results which are close to the measurements. The observed total energy release in photon emission per fission has been predicted by two published calculations which treated statistical evaporation theory in different ways to enhance the emission of photons. The $K$-shell x-ray intensities for the light- and heavy-fragment groups were found to be 0.08 ± 0.02 and 0.23 ± 0.02 photons/fission, respectively. The x-ray intensities are consistent with internal conversion of the observed $\gamma$-ray spectrum for various assumed mixtures of $E1\mathrm{}$, $E2\mathrm{}$, and $M2\mathrm{}$ transitions, including roughly equal $E1\mathrm{}-E2\mathrm{}$ mixtures; the intensities are not consistent with all the transitions having any single multipolarity.

The $\gamma$-singles and conversion-electron spectra of ${\mathrm{Fm}}^{255}$ were measured with a Ge(Li) diode and the Argonne double toroidal $\beta$-ray spectrometer, respectively. In the $\gamma$-ray spectra, in addition to the transitions expected from previously known decay schemes, $\gamma$ rays of energies 63.8, 131.8, 204.1, and 264.1 keV were observed. Two new $\alpha$ groups, ${\alpha }_{368}$ (6.765 MeV) and ${\alpha }_{433}$ (6.701 MeV), were identified in coincidence with 131.0- and 204.1-keV $\gamma$ rays. A two-parameter $\gamma -\gamma$ coincidence experiment showed that the 204.1- and 131.0-keV transitions populate the $\frac{9}{2}$ and $\frac{11}{2}$ members of the favored band. Conversion-electron studies and $\alpha -\mathrm{v}\mathrm{s}-\gamma$ intensity comparisons demonstrate their $E1\mathrm{}$ character. The half-life of the 370.4-keV level was measured by a delayed $\alpha -\gamma$ coincidence method and found to be 1.3 ± 0.1 μsec. On the basis of these observations and the $\alpha$ intensities to these levels, the 370.4- and 434.2-keV levels have been assigned to the $\frac{11}{2}-\left(725\mathrm{}\uparrow \right)$ and $\frac{9}{2}-\left(734\mathrm{}\uparrow \right)$ Nilsson states, respectively. A three-parameter $\alpha -\gamma$-time coincidence experiment indicates that the $\alpha$ intensity to the 105.73-keV ($I=\frac{7}{2},K=\frac{1}{2}$) level is less than 1%, implying that its 18% population comes primarily via a 0.57-keV transition from the 106.30-keV, $I=\frac{7}{2}$, $K=\frac{7}{2}$ level. The $\alpha$ transition probabilities to various bands are in agreement with the values expected from $\alpha$-decay systematics and theoretical calculations. The $K$-, $L$-, $M$-, and $N$-sunshell atomic electron binding energies in Cf ($Z=98\mathrm{}$), obtained experimentally by least-squares adjustment from the conversion-line data, show significant deviations below recent (Bearden and Burr) tabulated values.