Recent Articles

Determination of internuclear potentials from heavy-ion fusion excitation functions

J. R. Birkelund and J. R. Huizenga

Phys. Rev. C 17, 126 (1978) - Published 1 January, 1978

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The internuclear potential determined from published fusion barrier parameters is compared with the proximity potential of Blocki et al. Discussion is given of the uncertainties introduced into the data analysis by the effects of friction and errors in the barrier radii.

[NUCLEAR REACTIONS Fusion, determination of internuclear potentials from heavy-ion fusion excitation functions.]

Experimental study of the ${}^{20}{Ne}$ + ${}^{12}C$ system

H. Doubre, J. C. Roynette, E. Plagnol, J. M. Loiseaux, P. Martin, and P. deSaintignon

Phys. Rev. C 17, 131 (1978) - Published 1 January, 1978

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Excitation functions for elastic, inelastic, and four-particle transfer channels of the ${}^{12}C$ + ${}^{20}{Ne}$ system were measured from 17 to 35 MeV (c.m.). The elastic scattering data (excitation functions and angular distribution at 24.7 MeV) have been analyzed with the optical model. Elastic and inelastic scattering are also studied in the framework of the coupled-channel Born approximation. The results emphasize the importance of the $2^{+}$ state of ${}^{20}{Ne}$ in the description of the absorption. The comparison with the ${}^{16}O$ + ${}^{16}O$ system is discussed.

[NUCLEAR REACTIONS ${}^{12}C$ ( ${}^{20}{Ne}$ , ${}^{20}{Ne}$ ) ${}^{12}C$ measured excitation functions, $E_{c . m .} = 17 to 35$ MeV, $σ (θ)$ at 24.7 MeV; ${}^{12}C$ ( ${}^{20}{Ne}$ , ${}^{20}{Ne}^{*}$ ) ${}^{12}C$ and ${}^{12}C$ ( ${}^{20}{Ne}$ , ${}^{16}O$ ) ${}^{16}O^{*}$ measured excitation functions, $E_{c . m .} = 17 to 35$ MeV. Optical-model and coupled-channel analysis.]

Parity determinations in ${}^{105 - 109}{Cd}$ from linearly polarized gamma rays following ( ${}^{16}O, x n$ ) reactions

D. C. Stromswold, D. O. Elliott, Y. K. Lee, L. E. Samuelson, J. A. Grau, F. A. Rickey, and P. C. Simms

Phys. Rev. C 17, 143 (1978) - Published 1 January, 1978

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The linear polarization of $γ$ rays from the deexcitation of Cd isotopes $A = 105$ through 109 following ( ${}^{16}O, x n$ ) reactions were measured using a Ge(Li) Compton polarimeter. The linear polarizations are used with $γ$ -ray angular distributions to make unique-parity assignments and to remove ambiguity in angular-momentum values. With these measurements it is possible to identify many states in ${}^{105 - 109}{Cd}$ which are similar to states in Pd nuclei that have been interpreted as having one, two, or three quasiparticles coupled to a slightly deformed rotating core.

[NUCLEAR REACTIONS ${}^{92}{Zr} ({}^{16}O$ , $3 n γ)$ , $E = 58$ MeV; ${}^{94}{Zr} ({}^{16}O, 4 n γ)$ , $E = 63$ MeV; ${}^{94}{Zr} ({}^{16}O, 3 n γ)$ , $E = 59$ MeV; ${}^{96}{Zr} ({}^{16}O, 4 n γ)$ , $E = 56$ MeV; ${}^{96}{Zr} ({}^{16}O, 3 n γ)$ , $E = 56$ MeV. Linear polarization of ${}^{105 - 106}{Cd}$ $γ$ rays measured.]

Reactions of ${}^{20}{Ne}$ on ${}^{150}{Nd}$ at 175 MeV

M. L. Halbert, R. A. Dayras, R. L. Ferguson, F. Plasil, and D. G. Sarantites

Phys. Rev. C 17, 155 (1978) - Published 1 January, 1978

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Energy spectra of charged-particle reaction products from bombardment of ${}^{150}{Nd}$ by 175-MeV ${}^{20}{Ne}$ were measured with three $Δ E$ , $E$ telescopes at angles from 3.5° to 100°. The evaporation residues and symmetric-fission fragments were easily identified; their total cross sections were 1150 ± 90 and 280 ± 35 mb, respectively. The sum of these numbers is in good agreement with the fusion cross section predicted by the Bass model. The elastic cross section drops to ¼ of the Rutherford cross section at 30.4 ± 0.2° (lab), which implies that the total region cross section is 2.63 b. Products from quasielastic and from strongly damped collisions were observed; their angle-integrated yields account for the balance of the reaction cross section.

[NUCLEAR REACTIONS ${}^{150}{Nd}$ ( ${}^{20}{Ne}$ , ${}^{20}{Ne}$ ), ( ${}^{20}{Ne}, F$ ), ( ${}^{20}{Ne}, X$ ), $E = 175.3$ MeV; measured elastic, fission, fusion, evaporation residue $σ (θ)$ ; deduced total reacaction $σ$ .]

Scattering of polarized tritons by ${}^{9}{Be}$ and ${}^{12}C$

P. A. Schmelzbach, R. A. Hardekopf, R. F. Haglund, Jr., and G. G. Ohlsen

Phys. Rev. C 17, 16 (1978) - Published 1 January, 1978

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The differential cross section and the analyzing power $A_{y}$ for ${}^{9}{Be} (\vec{t}, t) {}^{9}{Be}$ and ${}^{12}C (\vec{t}, t) {}^{12}C$ elastic scattering have been measured at 15 and 17 MeV over the angular range $θ_{lab} = 17.5 - {165.0}^{\circ}$ . The data in the forward hemisphere have been analyzed with a standard optical model. A large depth and conventional geometry parameters for the spin-orbit potential have been found. The results of the present analysis are in general agreement with previous work involving polarized tritons scattered from heavy target nuclei and show important differences from investigations of the scattering of polarized helions on light nuclei.

[NUCLEAR REACTIONS ${}^{9}{Be} (\vec{t}, t) {}^{9}{Be}$ , ${}^{12}C (\vec{t}, t) {}^{12}C$ , $E = 15, 17$ MeV; measured $\frac{d σ}{d Ω} (θ)$ , $A_{y} (θ)$ ; deduced optical model parameters.]

Mass distributions in monoenergetic-neutron-induced fission of ${}^{238}U$

S. Nagy, K. F. Flynn, J. E. Gindler, J. W. Meadows, and L. E. Glendenin

Phys. Rev. C 17, 163 (1978) - Published 1 January, 1978

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Fission product yields for 44 masses were determined for the fission of ${}^{238}U$ with essentially monoenergetic neutrons of 1.5, 2.0, 3.9, 5.5, 6.9, and 7.7 MeV. Fission product activities were measured by Ge(Li) $γ$ -ray spectrometry of irradiated ${}^{238}U$ foils and by chemical separation of the fission product elements followed by $β$ counting and/or $γ$ -ray spectrometry. The mass-yield data for ${}^{238}U (n, f)$ show clearly the sensitive exponential increase of fission yields in the near-symmetric mass region (valley) with increasing incident neutron energy $E_{n}$ (peak-to-valley ratio decreasing from ∼600 to ∼40) over the range $E_{n} = 1.5 to 7.7$ MeV with little change in yields in other regions of the mass distribution. The valley yields plotted semilogarithmically as a function of $E_{n}$ reveal an abrupt change in slope at the onset of second-chance fission just above the neutron binding energy (at ∼6 MeV) where the excitation energy is lowered by competition with neutron evaporation prior to fission. Systematics are developed to permit synthesis of the mass distribution for any neutron energy in the range of 1.5 to 18 MeV.

[NUCLEAR REACTIONS, FISSION ${}^{238}U (n, f) E_{n} = 1.5, 2.0, 3.9, 5.5, 6.9, and 7.7$ MeV; measured mass yields.]

Charge distribution in the thermal-neutron-induced fission of ${}^{249}{Cf}$ : Independent and fractional cumulative yields of isotopes of Nb, I, and Cs

H. Gäggeler and H. R. von Gunten

Phys. Rev. C 17, 172 (1978) - Published 1 January, 1978

Show Abstract

The independent yields of ${}^{96}{Nb}$ , 51 min ${}^{98}{Nb}$ , ${}^{130}I^{g}$ , ${}^{136}{Cs}$ , and the fractional cumulative yield of ${}^{135}I$ were determined in the thermal-neutron-induced fission of ${}^{249}{Cf}$ . They were found to be [(4.4 ± 0.6) × $10^{- 3}$ ]%, (0.15 ± 0.03)%, [(3.1 ± 0.3) × $10^{- 2}$ ]%, (0.34 ± 0.02)%, and (3.3 ± 0.2)%, respectively; these values correspond to empirical $Z_{p}$ values of 38.92, > 39.41, > 51.04, 53.64, and 53.30, respectively, if a Gaussian charge dispersion function with a $σ$ of 0.56 is used. No odd-even nuclide corrections were applied in the calculation of $Z_{p}$ . A mean value for $Δ Z (= Z_{p} - Z_{UCD})$ of 0.45 ± 0.24 is obtained from all $Z_{p}$ values presently available in the thermal-neutron-induced fission of ${}^{249}{Cf}$ . The $Z_{p}$ values suggest a larger deviation from unchanged charge distribution for very asymmetric splits of the compound nucleus.

[RADIOACTIVITY, FISSION ${}^{249}{Cf} (n, f)$ ; measured $γ$ activity of fission products ${}^{96}{Nb}$ , 51 min ${}^{98}{Nb}$ , ${}^{130}I^{g}$ , ${}^{135}I$ , and ${}^{136}{Cs}$ . Ge(Li) detector, Radiochemical separations.]

${}^{35}{Cl}$ -induced fission and fissionlike reactions on ${}^{58, 62}{Ni}$ , ${}^{112, 116, 120, 124}{Sn}$ , and ${}^{141}\Pr$

J. Bisplinghoff, P. David, M. Blann, W. Scobel, T. Mayer-Kuckuk, J. Ernst, and A. Mignerey

Phys. Rev. C 17, 177 (1978) - Published 1 January, 1978

Show Abstract

Counter telescopes (gas $Δ E$ , Si-E) were used to measure angular distributions of binary yield products resulting from bombardment of ${}^{58, 62}{Ni}$ , ${}^{112, 116, 120, 124}{Sn}$ , and ${}^{141}\Pr$ targets with ${}^{35}{Cl}$ beams at energies between 155 and 170 MeV. Results are presented for angular distributions averaged over bins two atomic numbers wide and integrated over all fragment atomic numbers. The Sn and Pr targets give yields consistent with an equilibrium fission mechanism according to charge distributions, kinetic energies, and angular distributions. The interpretation of yields from Ni targets is found to be more ambiguous. All systems give fragment energies consistent with semiempirical trend formulas, independent of asymmetry. Qualitative evidence for deep inelastic yields, in addition to fission yields, are found for Sn and Pr targets.

[NUCLEAR REACTIONS ${}^{58, 62}{Ni}$ , ${}^{112, 116, 120, 124}{Sn}$ , ${}^{141}\Pr ({}^{35}{Cl}, f)$ ; measured fission product yields, fission product angular distributions, fission product mean kinetic energies, total fission cross sections; $E = 155 - 170$ MeV; gas proportional/solid state counter telescopes.]

Charge distribution in nuclear fission: Determination of fractional cumulative yields of ${}^{134}{Te}$ and ${}^{135}I$ in the spontaneous fission of ${}^{252}{Cf}$

S. B. Manohar, Tarun Datta, S. S. Rattan, Satya Prakash, and M. V. Ramaniah

Phys. Rev. C 17, 188 (1978) - Published 1 January, 1978

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The fractional cumulative yields of ${}^{134}{Te}$ and ${}^{135}I$ in the spontaneous fission of ${}^{252}{Cf}$ are determined by following the growth and decay of ${}^{134}I$ and ${}^{135}{Xe}^{g}$ activities, respectively, on a 60- ${cm}^{3}$ Ge(Li) detector. The values of the most probable charge ( $Zp$ ) for mass chains 134 and 135 are calculated assuming Gaussian distribution. The values of fractional cumulative yield are 0.791 and 0.975 for ${}^{134}{Te}$ and ${}^{135}I$ , respectively, and corresponding $Zp$ values are 52.03 ± 0.06 and 52.40 ± 0.06. The data are compared with other fractional cumulative yield values from literature in the spontaneous fission of ${}^{252}{Cf}$ to see the effect of fragment shells on the width of the charge distribution.

[RADIOACTIVITY, FISSION Spontaneous fission of ${}^{252}{Cf}$ : measured $γ$ activities ${}^{134}I$ and ${}^{135}{Xe}^{g}$ using Ge(Li) detector and obtained fractional cumulative yields; $Zp$ values for the mass chain 134 and 135 deduced.]

Deep inelastic pion-induced nuclear reactions in the isobar model

J. N. Ginocchio

Phys. Rev. C 17, 195 (1978) - Published 1 January, 1978

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Deep inelastic pion-induced nuclear reactions are calculated in the isobar model, which assumes that an interacting resonant pion and nucleon form an unstable particle, the $Δ$ , which can propagate through the nucleus and either decay or be absorbed by interacting with other nucleons in the nucleus. The propagation of the particles is treated classically and the interactions are assumed to be incoherent. The lifetime of the $Δ$ is taken to be energy dependent as prescribed by measured pion-nucleon scattering and the cross section of the $Δ$ absorption is determined by measured pion production in two nucleon collisions. The formation of the $Δ$ by a pion and nucleon and the subsequent absorption of the $Δ$ provide a two-step mechanism for pion absorption. These calculations indicate that the pion is absorbed mostly on the inside forward edge of the nuclear surface where the nuclear density has almost reached central density. The calculations are compared with measured pion absorption cross sections, proton spectra, and spallation products in pion-induced reactions. All of these data indicate that pion absorption is underestimated in this model by perhaps as much as 35%, particularly for low energy (∼ 100 MeV) pions. Possible explanations for these discrepancies are discussed.

[NUCLEAR REACTIONS Calculated absorption cross section, proton spectra, and spallation products for pion-induced reactions on various nuclei.]

Black sphere model for the linewidths of $P$ -state protonium

W. B. Kaufmann and H. Pilkuhn

Phys. Rev. C 17, 215 (1978) - Published 1 January, 1978

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The annihilation widths of $nP$ $\bar{p} p$ bound states (protonium) are calculated in the Wentzel-Kramers-Brillouin approximation for a totally absorbing sphere, including the coupling to $\tilde{n} n$ states. It is shown that the annihilation occurs preferentially in one of the two possible isospin eigenstates, and that on the average it is 100 times stronger than the radiative $2 P - 1 S$ transition. A simple formula for the $n$ dependence of the annihilation widths is also given.

[NUCLEAR REACTIONS. Protonium $\bar{p} p$ , calculated $p$ -state $Γ$ .]

Can relativistic pionic stripping explain ( $p, π^{+}$ ) reactions?

L. D. Miller and H. J. Weber

Phys. Rev. C 17, 219 (1978) - Published 1 January, 1978

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The relativistic pionic stripping formalism is used to study pion production data on ${}^{12}C$ and ${}^{40}{Ca}$ in order to determine the appropriate form of the pion-nucleon vertex and to determine whether pionic stripping is the dominant mechanism for pion production.

[NUCLEAR REACTIONS Proton induced pion production, relativistic pionic stripping, ${}^{12}C (p, π^{+}) {}^{13}C$ , ${}^{40}{Ca} (p, π^{+}) {}^{41}{Ca}$ ; calculated angular distributions, energy dependence (near threshold).]

Pion-induced single-nucleon removal to discrete final states

C. L. Morris, R. L. Boudrie, J. J. Kraushaar, R. J. Peterson, R. A. Ristinen, Gregory R. Smith, J. E. Bolger, W. J. Braithwaite, C. Fred Moore, and L. E. Smith

Phys. Rev. C 17, 227 (1978) - Published 1 January, 1978

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$γ$ radiation from targets of ${}^{7}{Li}$ , ${}^{9}{Be}$ , ${}^{12}C$ , ${}^{13}C$ , and ${}^{16}O$ bombarded by $π^{-}$ and $π^{+}$ at energies between 60 and 300 MeV was uniquely associated with states formed by removing a single nucleon by the ( $π, π N$ ) reaction. All yields were found to reflect the well-known 3-3 resonance near 180 MeV in the pion-nucleon system. Ratios of yields for $π^{-}$ and $π^{+}$ beams were measured for ${}^{7}{Li}$ , ${}^{9}{Be}$ , and ${}^{13}C$ . These ratios were very similar to one another and to previous results on ${}^{12}C$ , ${}^{14}N$ , and ${}^{16}O$ for neutron removal. Several reaction mechanisms based on quasifree processes are tested by comparison to the data, and all are rejected.

[NUCLEAR REACTIONS ${}^{7}{Li}$ , ${}^{9}{Be}$ , ${}^{12}C$ , ${}^{13}C$ , ${}^{16}O$ . ( $π^{\pm}, π N$ ), detect $γ$ decay of residual nucleus, measure $σ (E_{π})$ .]

Spin-dependent $N - N$ $t$ matrix for intermediate energy nucleon-nucleus reactions

A. Picklesimer and G. E. Walker

Phys. Rev. C 17, 237 (1978) - Published 1 January, 1978

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A nucleon-nucleon transition matrix fitted to the 50-400 MeV differential cross section and polarization data is presented. The transition operator obtained is a sum of spin- and isospin-dependent central, two-particle spin-orbit, and tensor complex local interactions with Yukawa radial shapes. The application of the transition operator is illustrated and discussed for medium energy nucleon-nucleus inelastic scattering. A comparison is made of the inelastic scattering results with results obtained for electron, pion, and kaon probes. The importance of exchange even at medium energies is stressed. The derived $N - N$ transition operator can be employed in microscopic polarization predictions and is appropriate for explicitly calculating exchange effects.

[NUCLEAR REACTIONS Deduced nucleon-nucleon transition matrix from two body data. ${}^{16}O (p, p^{'})$ , $E = 156$ MeV; ${}^{28}{Si} (p, p^{'})$ , $E = 134$ MeV; calculated $σ (θ)$ . Comparison with electron, kaon, and pion results.]

Trinucleon photoeffect to isospin 3/2, using coupled hyperspherical harmonics

K. K. Fang, J. S. Levinger, and M. Fabre de la Ripelle

Phys. Rev. C 17, 24 (1978) - Published 1 January, 1978

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We extend the Fabre-Levinger calculation of the ${}^{3}{He}$ photoeffect ( $E 1$ transition to final isospin 3/2) by including an additional grand orbital ( $L = 3$ ) in the final state wave function. The coupled differential equations between $L = 1$ and $L = 3$ for the final state are given. We solve for two model potentials, and find the Blatt-Biedenharn eigenphase shifts and the mixing parameter, and also the total cross section for photodisintegration. We find reasonable agreement (generally within 10%) with the cross section found for one hyperspherical harmonic. The convergence speed of the hyperspherical harmonic expansion for the outgoing channel is also examined by comparison with sum rules for the integrated cross section: We find rapid convergence for both models.

[NUCLEAR REACTIONS Photodisintegration of trinucleon system, coupled hyperspherical harmonics.]

Pion-nucleon form factor in the Chew-Low theory

D. J. Ernst and Mikkel B. Johnson

Phys. Rev. C 17, 247 (1978) - Published 1 January, 1978

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We find a solution to the static Chew-Low theory of pion-nucleon scattering, avoiding the "one-meson approximation." Our basic equation is crossing symmetric and may be solved for phase shifts $δ (p)$ by standard numerical techniques, upon specifying a form factor $ν (p)$ and a set of inelasticities. With $ν (p) = \exp (\frac{- p^{2}}{30})$ we reproduce experimental $δ (p)$ for $p_{L} \leq 1.2 \frac{GeV}{c}$ in the (3,3) state; in the (1,3) states and (3,1) states $δ (p)$ compare well on the average but in the (1,1) state $δ (p)$ have opposite signs. We show the importance of crossing symmetry and the coupling to inelastic channels, and we discuss the possibility of determining $ν (p)$ directly from elastic scattering by an inverse scattering formula.

[NUCLEAR REACTIONS Pion-nucleon elastic scattering; Chew-Low theory, pion nucleon form factor, crossing symmetry, coupling to inelastic channels, inverse scattering problem.]

Pion production from the $pd \to d π^{+} n$ reaction at 585 MeV

K. R. Hogstrom, G. S. Mutchler, T. R. Witten, J. Hudomalj-Gabitzsch, J. M. Clement, R. D. Felder, W. H. Dragoset, W. P. Madigan, J. A. Buchanan, G. C. Phillips, E. V. Hungerford, B. W. Mayes, L. Pinsky, L. Y. Lee, T. M. Williams, and J. C. Allred

Phys. Rev. C 17, 259 (1978) - Published 1 January, 1978

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Pion production from the reaction ${}^{2}H (p, d π^{+}) n$ was measured in a kinematically complete experiment at an incident proton energy of 585 MeV. The deuteron was detected with a magnetic spectrometer fixed at 35°. The pion was detected at seven angles from 30° to 90° lab angle. The data exhibit a broad peak in the deuteron momentum spectrum that decreases in magnitude and shifts to greater momentum with increasing pion angle.

[NUCLEAR REACTIONS ${}^{2}H (p, d π^{+}) n$ , $E = 585$ MeV; measured $\frac{d^{5} σ}{d p_{1} d Ω_{1} d Ω_{2}}$ .]

High energy collisions between nuclei and correlations

Girish K. Varma

Phys. Rev. C 17, 267 (1978) - Published 1 January, 1978

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We investigate the effects of correlations on high energy collisions between nuclei. New types of multiple scattering can occur in such collisions and their contributions to cross sections are shown to depend significantly on the presence (or absence) of short range correlations. Nucleus-nucleus collisions may, therefore, be able to probe such correlations. Calculations are performed for ${}^{12}C$ - ${}^{12}C$ and ${}^{16}O$ - ${}^{16}O$ elastic scattering, using correlation lengths obtained from nuclear matter calculations. The effects of short range correlations are found to be significant and, in the case of collisions between heavy nuclei, their presence prevents the higher order corrections to the optical phase shift function from taking unphysical values at small impact parameters.

[NUCLEAR REACTIONS Nucleus-nucleus scattering, $E = 2.1 \frac{Gev}{n}$ ; correlation effects.]

Spectroscopy of the ${}^{108}{In}$ nucleus

H.-C. Hseuh and E. S. Macias

Phys. Rev. C 17, 272 (1978) - Published 1 January, 1978

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The $γ$ rays following the $β$ decay of 10.30-min ${}^{108}{Sn}$ and from the in-beam ${}^{108}{Cd} (p, n) {}^{108}{In}^{*} (γ)$ reaction between 6.5 and 10 MeV have been studied in order to determine the properties of the low-lying levels of ${}^{108}{In}$ . Twenty-five $γ$ rays attributed to ${}^{108}{Sn}$ decay were observed. A level scheme of ${}^{108}{In}$ was constructed which contains nine levels, of which only three were previously reported. Spin and parity values are assigned to each level based on angular distribution and excitation function measurements from the ( $p, n γ$ ) reaction and $log ft$ values from ${}^{108}{Sn}$ decay. The level properties of ${}^{108}{In}$ are compared to the levels of ${}^{94}{Nb}$ and interpreted within the framework of $j - j$ coupling.

[RADIOACTIVITY ${}^{108}{Sn}$ [from ${}^{106}{Cd} (α, 2 n)$ ], enriched target. Measured $t_{\frac{1}{2}}$ , $E_{γ}$ , $I_{γ}$ , $γ - γ$ coin; deduced ${}^{108}{In}$ levels, $J$ , $π$ , and $log ft$ values. Ge(Li) detectors, Ge(Li)-NaI(T1) anti-Compton spectrometer.]

[NUCLEAR REACTIONS ${}^{108}{Cd} (p, n) {}^{108}{In}^{*} (γ)$ , $E_{p} = 6.5 - 10$ MeV, enriched target. Measured $E_{γ}$ , $I$ , $I_{γ} (θ)$ ; deduced ${}^{108}{In}$ levels, $δ (\frac{E 2}{M 1})$ , $J$ , $π$ , branching fractions; Ge(Li) detectors, Ge(Li)-NaI(T1) anti-Compton spectrometer.]

Beta-ray branching and half-lives of ${}^{12}B$ and ${}^{12}N$

D. E. Alburger and A. M. Nathan

Phys. Rev. C 17, 280 (1978) - Published 1 January, 1978

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The ratio of ${}^{12}B$ and ${}^{12}N$ $β$ -ray branches to the 4.44-MeV excited state of ${}^{12}C$ was measured by detecting $β$ rays in a $4 π$ plastic scintillator and $γ$ rays in two Ge(Li) detectors. Activities were made in the ${}^{11}B (d, p) {}^{12}B$ and ${}^{10}B ({}^{3}{He}, n) {}^{12}N$ reactions using a chopped Van de Graaff beam. Data were stored in two successive computer time bins of two half-lives each in order to establish by subtraction the shape of the short-lived $β$ -ray spectrum and its net number of counts. The ratio of these branches was found to be ${}^{12}N$ / ${}^{12}B$ = 1.56±0.05. A measurement of the ${}^{12}B$ absolute $β$ -ray branch to the 4.44-MeV state via $β - γ$ coincidences using an NaI(T1) detector for the $γ$ rays gave a value of 1.276±0.050%. Half-lives, obtained by multiscaling $β$ -ray counts, were found to be 20.20±0.02 msec for ${}^{12}B$ and 11.000±0.016 msec for ${}^{12}N$ . The mirror asymmetries derived from these results are $δ = + 0.044 \pm 0.034$ for the decay to the 4.44-MeV state of ${}^{12}C$ and $δ = + 0.129 \pm 0.008$ for the branch to the ground state.

[RADIOACTIVITY ${}^{12}B$ , ${}^{12}N$ : Measured $I_{β}$ , $I_{γ}$ , $β - γ$ coin, $T_{\frac{1}{2}}$ ; deduced $β$ -ray branches, mirror asymmetries.]

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Determination of internuclear potentials from heavy-ion fusion excitation functions

Experimental study of the ${}^{20}{Ne}$ + ${}^{12}C$ system

Parity determinations in ${}^{105 - 109}{Cd}$ from linearly polarized gamma rays following ( ${}^{16}O, x n$ ) reactions

Reactions of ${}^{20}{Ne}$ on ${}^{150}{Nd}$ at 175 MeV

Scattering of polarized tritons by ${}^{9}{Be}$ and ${}^{12}C$

Mass distributions in monoenergetic-neutron-induced fission of ${}^{238}U$

Charge distribution in the thermal-neutron-induced fission of ${}^{249}{Cf}$ : Independent and fractional cumulative yields of isotopes of Nb, I, and Cs

${}^{35}{Cl}$ -induced fission and fissionlike reactions on ${}^{58, 62}{Ni}$ , ${}^{112, 116, 120, 124}{Sn}$ , and ${}^{141}\Pr$

Charge distribution in nuclear fission: Determination of fractional cumulative yields of ${}^{134}{Te}$ and ${}^{135}I$ in the spontaneous fission of ${}^{252}{Cf}$

Deep inelastic pion-induced nuclear reactions in the isobar model

Black sphere model for the linewidths of $P$ -state protonium

Can relativistic pionic stripping explain ( $p, π^{+}$ ) reactions?

Pion-induced single-nucleon removal to discrete final states

Spin-dependent $N - N$ $t$ matrix for intermediate energy nucleon-nucleus reactions

Trinucleon photoeffect to isospin 3/2, using coupled hyperspherical harmonics

Pion-nucleon form factor in the Chew-Low theory

Pion production from the $pd \to d π^{+} n$ reaction at 585 MeV

High energy collisions between nuclei and correlations

Spectroscopy of the ${}^{108}{In}$ nucleus

Beta-ray branching and half-lives of ${}^{12}B$ and ${}^{12}N$

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