As3d core level studies of (GaMn)As annealed under As capping

The surface of a Ga_0.95Mn_0.05As layer subjected to low temperature annealing under As capping has been studied by core level photoemission with focus on As3d spectrum. By detailed comparison with the surface of pure GaAs subjected to the same surface treatment, the As spectral component of the reacted surface layer has been identified. The relative intensity of this component is consistent with the notion of an MnAs monolayer terminating the annealed (GaMn)As surface.     

Energy levels in As from the As(p,d) As reaction

The ⁷⁵As(p, d) ⁷⁴As reaction has been used to identify 23 excited states in ⁷⁴As. The l_n values, or mixture of l_n values, to 19 levels have been determined from DWBA fits. The spectroscopic sum rules show a neutron shell filling which is consistent with other N = 42 isotones.     

The decay of84As

The decay properties of⁸⁴As have been investigated with mass separated sources. Only one β-decaying state is seen, contradictory to previous observations. The halflife is found to be 4.5±0.2 s. A detailed decay scheme has been constructed, and 33 excited states in⁸⁴Se have been determined.     

Level structure of 76As

The energy-level structure of ⁷⁶As has been studied by the ⁷⁵As(d, p) reaction with 12.0 MeV incident deuterons. Eighty-seven excited energy levels up to 2.5 MeV have been identified. The angular distributions for thirty-nine of the observed transitions are compared with distorted-wave Born approximation calculations. Angular momentum transfers are determined and spectroscopic strengths are deduced from the data. The results are compared with shell-model sum rules and with (d, p) results on N = 42 isotones. Possible spin values are assigned for some of the levels based on the present results, (n, γ), (p, n) and (p, nγ) studies.     

The decay of85As

The decay of isotope-separated⁸⁵As has been studied for the first time by means ofγ-ray spectroscopy. A level scheme for⁸⁵Se has been constructed on the basis ofγγ-coincidence measurements. Spin and parity were then assigned to the lowest excited levels. Two levels, weakly populated in⁸⁴Se after emission of delayed neutrons, were also identified. The results obtained here differ considerably from previously reported experiments with chemically separated sources.     

Hawking radiation As tunneling

We present a short and direct derivation of Hawking radiation as a tunneling process, based on particles in a dynamical geometry. The imaginary part of the action for the classically forbidden process is related to the Boltzmann factor for emission at the Hawking temperature. Because the derivation respects conservation laws, the exact spectrum is not precisely thermal. We compare and contrast the problem of spontaneous emission of charged particles from a charged conductor.     

Effect of Ga and As vacancies on electronic properties of Ga0.9375Al0.0625As

Electronic properties of Ga_0.9375Al_0.0625As with Ga and As monovacancies are investigated with the density functional theory. A perfect GaAlAs, which specifically produces a radiation wavelength of ～825.6 nm, has been determined in terms of size and number of atoms of substances. We have introduced eight types of vacancies depending on the distance from the Al atom to the vacancy to obtain the changes in charges, band structures, density of states, and optical conductivity. We found that the Fermi level enters into the valence band due to the formations of the Ga or As vacancies so that the vacant materials may show the characteristics of the p-type semiconductor. Interestingly, Ga-vacancy systems make direct band gaps, which are still good for the use in a semiconductor laser. But, As-vacancy systems, where the indirect gaps appear, are not feasible for the same application. It has been found that the latter phenomenon is induced by a newly formed density of state, which comes from the overlapping of hybridised 4s and 4p orbitals of Ga atoms around As vacancy.     

Multiphonon absorption in As2S3As2Se3 glasses

Multiphonon absorption in As₂S₃ and As₂Se₃ glasses is well explained by a molecular model in terms of combination bands of high frequency vibrational modes of pyramidal AsY₃ and bent AsYAs groups (Y = SorSe). Multiphonon absorption coefficients in mixed As₂S₃As₂Se₃ glasses are nearly additive in terms of the pure components, suggesting a high degree of non-random mixing.     

The decay of 91 min As

The energies and relative intensities of γ-rays following the β-decay of ⁷⁸As (and ⁷⁶As) to levels in ⁷⁸Se (and ⁷⁶Se) have been measured using an 8 cm³ Ge(Li) spectrometer. The β-decay of ⁷⁸As has been measured using a superconducting magnet beta-ray spectrometer with two 3 mm thick Si(Li) detectors. These data plus β-γ and γ-γ coincidence results have been used to construct a level scheme with 18 excited levels in ⁷⁸Se. The half-life of ⁷⁸As was measured to be 90.7±0.2 min.     

On-line nuclear orientation of70As

On-line nuclear orientation was performed on⁷⁰As. Anisotropy data have been obtained at 8.7mK for 29 gamma transitions. Multipole mixing ratios have been extracted for 17 transitions. Our results are in good agreement with existing data for the ten previously measured transitions. Our first time data for the 1496 keV, 2⁺→2⁺ γ-ray suggest the 2536 keV level is a good candidate for a mixed symmetry level.     

Electronic Structure of InCo2As2 and KInCo4As4: LDA + DMFT

JETP Letters - A comparative analysis of the electronic structure obtained in the DFT/LDA and LDA + DMFT approaches of the possible isostructural analogues of iron superconductors InCo2As2 and...     

Decoupled band in73As

Using the (α, 2nγ) reaction we have established a partial decay scheme of⁷³As. A positive parity band built on the 428 keV 9/2⁺ level is interpreted as a decoupled band.     

Core-excitation calculations in75As

The nuclear properties of the low-lying negative parity states in⁷⁵As are discussed in terms of the excited-core model. The core and particle parameters were determined by a simultaneous fitting of the available data into a least square iteration program.     

Supersymmetry in74Se,75Se,73As,and74As nuclei

New experimental data, obtained on⁷³As and⁷⁴As, were used to test the predictions of the U(6/12)U (6/12) supersymmetry scheme in its vibrational limit. The level spectra of ₃₄ ⁷⁴ Se₄₀, ₃₄ ⁷⁵ Se₄₁, ₃₃ ⁷³ AS₄₀ and ₃₃ ⁷⁴ As₄₁ supermultiplet nuclei have been calculated using a simple closed energy formula. 44 states in four different nuclei have been reasonably described using only 7 fitted parameters. The existence of supersymmetry was supported also by one-nucleon transfer reaction data, electromagnetic properties, and by a comparison between the supersymmetry and interacting boson-fermion-fermion model wave functions.     

The electronic structure of modulation-doped In0.53Ga0.47As/n-In0.52Al0.48As heterostructure

Summary The subband structure of modulation-doped InGaAs/InAlAs heterostructures is calculated in a variational self-consistent manner. The dependence on various device parameters is examined. The many-body exchange correlation effects are taken into account.     

A study of low-lying states of 76As using the 75As(d,p) reaction

The ⁷⁵As(d, p)⁷⁶As reaction was investigated with 11 MeV deuterons. Thirty levels of the residual nucleus were identified up to about 1.8 MeV excitation energy, and angular distributions were measured. Spectroscopic factors and l_n values were obtained for low-lying transitions by means of a distorted-wave analysis of the differential cross sections. The l_n = 4 transition to the ground state of ⁷⁶As and the presence of l_n = 2 transitions to low-lying levels provide a strong support to the assumption that nuclei in this mass region have a large deformation parameter. The results are compared with the ⁷⁵As(n, γ)⁷⁶As data.