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Polarized magneto-photoluminescence (MPL) measurements on a high mobility {delta}-doped GaAs/AlGaAs single quantum well from 0--60 T at temperatures between 0.37--2.1 K are reported. In addition to the neutral heavy hole magneto-exciton (X{sup 0}), the singlet (X {sub s}{sup {minus}}) and triplet (X {sub t}{sup {minus}}) states of the negatively charged magneto-exciton are observed in both polarizations. The energy dispersive and time-resolved MPL data suggest that their development is fundamentally related to the formation of the neutral magneto-exciton. At a magnetic field of 40 T the singlet and the triplet states cross as a result of the role played by the higher Landau levels and higher energy subbands in their energetic evolution, confirming theoretical predictions. The authors also observed the formation of two higher energy peaks. One of them is completely right circularly polarized and its appearance can be considered a result of the electron-hole exchange interaction enhancement with an associated electron g-factor of 3.7 times the bulk value. The other peak completely dominates the MPL spectrum at fields around 30 T. Its behavior with magnetic field and temperature indicates that it may be related to previous anomalies observed in the integer and fractional quantum Hall regimes.

dHvA measurements have been made on the 32 Kelvin cubic superconductor Ba 0.6 K 0.4 BiO 3 (BKBO) using a new and non-destructive 50 Tesla pulsed field magnet at the NHMFL at Los Alamos, as well as in an 18 T superconducting magnet at Louisiana State University. Data were taken with the magnetic field aligned along the [001] crystallographic direction. Sample temperatures were varied from 1.5 to 3.9 Kelvin. The pulsed fields employed were high enough to drive the system well into the normal state. An analysis of these results showed that the frequencies of the observed dHvA oscillations arose from a several Fermi surface sheets. One cross-section was nearly identical with that predicted by a new LDA band calculation.

$\ensuremath{\gamma}$-ray transitions from states in $^{50}\mathrm{V}$ up to 1680 keV excitation have been studied using the ($p,n\ensuremath{\gamma}$) reaction. Branching ratios and some lifetime information was obtained. There is an indication of a doublet at 910 keV, the existence of which is previously unreported. Relative transition probabilities are compared to the $1{f}_{\frac{7}{2}}$ model of $^{50}\mathrm{V}$.

The $g$ factor of the 738 keV second excited state in $^{43}\mathrm{K}$ has been measured using a perturbed angular correlation technique. A value for the half-life was also obtained. The level was populated via the $^{40}\mathrm{Ar}(\ensuremath{\alpha},p)^{43}\mathrm{K}$ reaction at 15 MeV with a pulsed beam. The spin precession was measured in an external magnetic field of \ensuremath{\sim} 3.8 and 5.4 kOe. The measured $g$ factor is + 1.28 \ifmmode\pm\else\textpm\fi{} 0.04, which is consistent with the reported spin of ${7/2}^{\ensuremath{-}}$. A comparison of the $g$ factor with other ${7/2}^{\ensuremath{-}}$ states in the odd potassium isotopes, and the ground state moments of the odd scandium isotopes reveal the state to be predominantly single particle in nature.

A comparison is made between the yield curves of the measured /sup 52/Cr(..cap alpha..,..gamma../sub 0/) and /sup 55/Mn(p,..gamma../sub 0/) reactions in the giant dipole resonance region of /sup 56/Fe (E/subx/=14.0 to 21.5 MeV) to determine if the gross differences can be interpreted as being due to isospin effects. Above 18 MeV the yield of (..gamma..,..cap alpha../sub 0/), determined by the principle of detailed balance, is observed to drop below the value obtained when the energy dependence of the transmission coefficients is removed. This leads to the conclusion that while the diminished yield in the (..gamma..,..cap alpha../sub 0/) channel may be due to the failure to populate the isospin forbidden T/sub greater-than/ states, other effects cannot be ruled out. (AIP)

The mean lifetimes of levels in 55Co below 5.2 MeV have been investigated with the Doppler-shift attenuation method and the 54Fe(3He, d)55Co reaction at 12 MeV. Scattered particles were detected in two E-ΔE telescopes at ±55° with respect to the beam axis, in coincidence with γ-rays observed at 90° and 130° in a 50 cm3 Ge(Li) detector. Mean lifetimes are reported for the following levels (energy in keV, lifetime in fs): 2166 (139±18), 2566 (680±200), 2923 (>245), 2939 (190±65), 3303 (99±22), 3323 (54±15), 3642 (680−300+400), 3943 (>170), 4164 (54±15), 4180 (

We have measured the cross sections and the analyzing powers for the $^{14}\mathrm{C}(\stackrel{\ensuremath{\rightarrow}}{p}, \ensuremath{\gamma})^{15}\mathrm{N}$ reaction for proton energies from 4.0 to 16.2 MeV. The corresponding range in excitation energies, 13.94 to 25.33 MeV, covers the region of the giant dipole resonance in $^{15}\mathrm{N}$. The five-angle angular distributions measured with unpolarized and with polarized beams at eight energies over this region were analyzed to determine the magnitudes and relative phases of the transition matrix elements. The analysis included $E1$, $M1$, and $E2$ transitions. The observed $E1$ strength exhausts only about 6% of the classical dipole sum rule. The dominant $E1$ strength is compared to a shell-model calculation which includes 3p-3h excitations. A fairly uniform distribution of $E2$ strength is observed which exhausts about 7% of the total energy-weighted sum rule. Although large uncertainties on this result could allow the existence of a giant $E2$ resonance, the most probable values indicate that no appreciable concentration of $E2$ strength is observed.

The angular distributions of cross sections and analyzing powers have been measured for the /sup 58/Fe(p, ..gamma../sub 0/)/sup 59/Co reactions throughout the giant dipole resonance regions of /sup 55/,/sup 57/,/sup 59/Co. In addition, the 90degree yield curve has been measured for the /sup 58/Fe(p, ..gamma../sub 0/)/sup 59/Co reaction for E/subp/ from 5.0 to 16.0 MeV in 100 keV steps. The data are analyzed to deduce the amplitudes and phases of the T matrix elements involved. The preferred solution indicates that the major change occurring in crossing the giant dipole resonance occurs in the relative phase between the d/sub 5///sub 2/ and g/sub 9///sub 2/ amplitudes. The implications of these results are discussed vis a vis the isospin splitting of the giant dipole resonance. (AIP)

Levels of 48 V were populated by the 48 Ti(p, nγ) and the 34 S( 16 O, pnγ) reactions. Proton energies of 5.5, 6.0, 6.4 and 7.0 MeV and a 16 O energy of 34 MeV were used. Gamma rays were measured in singles. The J π assignments for eight of these levels follows from γ-ray angular distribution and linear polarization measurements when combined with presently available lifetime and nucleon transfer data.

The 90/sup 0/ yield curves for the /sup 30/Si( p,..gamma../sub 0/)/sup 31/P and /sup 30/Si( p,..gamma../sub 1/)/sup 31/P reactions have been measured for E/sub p/=5.0 to 28.0 MeV. Angular distributions of cross section and analyzing power were obtained at twelve energies between E/sub p/=6.36 and 14.45 MeV. The cross sections were measured at nine angles between 30/sup 0/ and 154/sup 0/, the analyzing power at seven angles between 42/sup 0/ and 142/sup 0/. For the case of ( p,..gamma../sub 0/) the complex T-matrix elements were extracted, assuming that the angular distributions are governed by coherent E1 and E2 processes. Two sigma(E2) yield curves are obtained, one of which exhausts 9--12% of the ..delta..T=0 E2 energy weighted sum rule while the other exhausts 21--31%. The results are compared to direct-semidirect model calculations which suggest that the larger E2 cross sections are the physical solutions.

Linear polarizations of ..gamma.. rays from the 11.86 ..-->.. 8.12 ..-->.. 4.12 MeV decay in /sup 2/4Mg have been studied with a NaI polarimeter. The 11.86 MeV level was populated via the /sup 1/2C(/sup 1/6O,..cap alpha gamma..)/sup 2/4Mg reaction. The results are consistent with J/sup ..pi../ = 8/sup +/ for the 11.86 MeV level and in agreement with earlier work, rule against a 6/sup +/ assignment with 85% confidence.

The /sup 40/Ca(d, ..cap alpha..)/sup 38/K reaction has been studied with tensor polarized deuterons using an annular detector at 180degree. These measurements allow a 0/sup -/ assignment to be made to the 2.99-MeV level in /sup 38/K. (AIP)

Previous workers1) have measured 54,56Fe(p,γo) cross sections in the giant dipole resonance region of 55Co and 57Co. We have extended this work2) by measuring the angular distributions of the analyzing power for the \( ^{54,56}Fe\left( {\vec p,{\gamma _o}} \right) \) reactions through the GDR region. In addition, both cross section and analyzing power measurements have been obtained from the \( ^{58}Fe{\left( {p,{\gamma _o}} \right)^{59}}Co \) reaction. The 90° yield curve for the inverse reaction is shown in Fig. 1. These three reactions, with target isospins of T= 1, 2 and 3 provide a means for examining the isospin splitting and the relative strengths of the T components of the GDR as a function of T.

It is shown that the recent J/sup pi/ = 3/2/sup +/ assignment for the level observed in the /sup 14/C(p, ..gamma../sub 0/)/sup 15/N reaction at E/subp/ = 6.925 MeV is not unique. (AIP)

Thin self-supporting beryllium foils preparation for use as atomic and molecular ion beam targets