Polarization effects in the photoemission spectra of trigonal tellurium

Strong and unequivocal polarization effects are observed on the photoemission spectra of vacuum-cleaved, $\text{(10}\text{1}\text{0)}$ Tellurium. Calculations of the energy distribution curves of the photoelectrons have been performed based on pseudopotential band structure and wave functions. The results correlate with the observations and allow for the interpretation of the measured EDC in terms of bulk properties and surface effects.     

Polarization transfer in deuteron stripping reactions

Polarization phenomena involving the spins of a and b in the A(a, b)B reaction are discussed using a complete set of irreducible tensors carrying definite spin transfer. The linear model independent equations relating the cross section and the polarization observables with these tensors are shown to be particularly appropriate for the study of spin dependent interactions, preferentially associated with particular values of spin transfer. The DWBA theory of polarization transfer in deuteron stripping reactions is thoroughly discussed and among the 17 polarization observables we distinguish those likely to be more sensitive to spin dependent distortion, to have stronger deuteron D-state effects, to exhibit the sign-rule j-dependence and other forms of j-dependence. For certain deuteron polarizations, when the spin transfer is pure $\text{s =}\text{1}\text{2}$, it is shown that deuteron stripping reactions are transparent to vector polarization transfer and the outgoing nucléon polarization independent of scattering angle and deuteron energy. DWBA calculations including contributions from spin transfer $\text{3}\text{2}$ through the deuteron D-state and spin-orbit distortion show that polarization transfer in such deuteron polarizations can be explored as a method of producing fast polarized neutrons with known polarization.     

Transparency to vector polarization transfer in deuteron stripping reactions

For certain deuteron polarizations, when the spin transfer is pure $\text{s =}\text{1}\text{2}$, it is shown that deuteron stripping reactions are transparent to vector polarization transfer and the outgoing nucleon polarization independent of scattering angle and deuteron energy. With $\text{s =}\text{3}\text{2}$ contributions there is still considerable transparency at the stripping main peak in DWBA calculations.     

Correlations and spin susceptibility of lowst-energy Cooper pairing in an antiferromagnet

Lowest-energy Cooper pairing of electron eigenfunctions in an antiferromagnetic metal is transformed to $\text{k}$-wave or nonmagnetic-Bloch-function space, where the pairing is resolved into wave-vector and spin components. The spin susceptibility is calculated using an eight-component field in Bloch function space.     

Observation of a high spin polarization of secondary electrons from single crystal Fe and Co

The spin polarization of secondary electrons with nearly zero kinetic energy from Fe (100) and Co (10$\text{1}$0), excited with photons of energy between 20 and 60 eV, was found to be 45%±5% for Fe and 35%±5% for Co. This value is higher than the average valence band spin polarization P_b=n_b/n=2.2/8=27% and 1.7/9=19% for Fe and Co, respectively. With increasing kinetic energy, the spin polarization of the secondaries decreases to the value of P_b within the first 5 eV, remaining constant (within statistical error) at higher kinetic energies. As a spin dependent scattering process we propose excitations within the d-bands, which can be shown to be asymmetric with respect to the electron spin. The high net spin polarization of the slowest emitted electrons is obtained by filtering out monitory-spin electrons at the vacuum barrier.     

The zero field Kondo susceptibility at lower temperatures

The zero field impurity spin susceptibility is calculated for spin $\text{1}\text{2}$ Kondo systems. By taking into account the self energy of the transverse impurity spin excitations the previous selfconsistent approximation is modified such that the unitarity bound for spin wave scattering is taken care of. For lower temperatures an improvement for the static susceptibility is achieved.     

Determination of effective interaction between two plasmons

Using the Bohm-Pines hamiltonian the problem of the bound state of two plasmons is investigated following two different decoupling procedures where the energy transfer $\text{Ω = 0}$ or 2ω_pl. The effective interaction g₄ between the two plasmons is found to be repulsive for $\text{Ω = 2ω}{}_{\mathrm{pl}}$ and attractive when $\text{Ω = 0}$. The case of $\text{Ω= 2ω}{}_{\mathrm{pl}}$ is shown to be analogous to the situation under which the critical coupling g_4c is determined.     

The polarization of a spin one half Kondo impurity at intermediate temperatures

A selfconsistent perturbation calculation for the impurity spin polarization and susceptibility as function of temperature and applied magnetic fields is carried out within the Tomonaga model for spin $\text{1}\text{2}$ Kondo systems.     

Splitting of the conduction bands of GaAs for k along [110]

The splitting of the spin degeneracy of the lowest conduction band of GaAs for $\text{k}$ along [110] is calculated by $\text{k}$·$\text{p}$ perturbation theory as well as by means of the self-consistent LMTO method. The magnitude and the sign of the calculated splitting agree with recent measurements of the spin precession in spin- polarized photoemission from GaAs [110] surfaces.     

On the rigorous determination of the spin-0-spin-12 elastic scattering amplitudes from experimental data and unitarity

The contraction-mapping principle is used to study rigorously the elastic unitarity equations for the scattering of a spin-0 particle by a $\text{spin}\text{-}\text{1}\text{2}$ particle when the unpolarized differential cross section dσ/dΩ and the polarization P at fixed energy below the first inelastic threshold are known from experiment. It is shown that when dσ/dΩ, P and the region where the scattering amplitudes are searched are suitably restricted, the scattering amplitudes exist, are unique and can be found by iterating the unitary equations. Besides, there are other solutions outside that space associated with well-known ambiguities. We show that those ambiguities are solved by measuring the parameters R and A and the sign of the real part of the forward amplitude.     

The spin polarization of conduction electrons in ferromagnetic semiconductors

Within the framework of the s?f exchange model the exact asymptotics of the spin polarization of conduction electrons in the non-degenerate ferromagnetic semiconductor at low temperatures is calculated. It is demonstrated that the temperature dependent corrections to the total density of states are proportional to $\text{T}{}^{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$.     

On a possible test of massive high spin wave equations in heavy-ion scattering

Cross sections and polarization functions for elastic scattering of identical particles with spin 1 are compared in the relativistic $\text{(s,0)+(s?}\text{1}\text{2}\text{,}\text{1}\text{2}\text{)}$ invariant theory, for arbitrary spin, and the $\text{(}\text{1}\text{2}\text{,}\text{1}\text{2}\text{)}$ invariant Proca theory. Heavy-ion scattering is suggested to test high spin theories.     

Magnetic moments of 112− states in the Sn region

The relative differences of eight magnetic moments of $\text{11}\text{2}\text{?}$ states in the Sn region are excellently reproduced by first-order core polarization effects calculated with the use of experimentally known energy denominators and occupation numbers.     

Photoelectron diffraction effects in XPS angular distributions from GaAs(110) and Ge(110) single crystals

Angular distribution measurements of XPS intensities have been made for various spectral lines from GaAs(110) and Ge(110) single-crystal surfaces. Observed angular distribution curves (ADC's) showed steep intensity variations and sharp peaks due to X-ray photoelectron diffraction (XPED) phenomena. The effects of the type of transition process (photoelectron or Auger), electron kinetic energy and crystal structure on the XPED patterns were examined. Considerably different ADC patterns were observed for high-energy photoelectrons and Auger electrons and for low-energy photoelectrons. ADC's for Ga 3d, As 3d and Ge 3d showed almost the same patterns for scans of the type [110] → [100] → [1$\text{1}$0], but they showed substantially different patterns for [110] → [11$\text{1}$] → [00$\text{1}$] scans. These features correspond well with the structural characteristics of GaAs and Ge crystals. A discussion of the applicability of XPS angular distribution measurements to the geometric analysis of crystal surfaces is presented.     

Polarization dynamics for spin 12-spin I systems with Breit-Rabi interaction

We study the full polarization dynamics of two interacting systems of spin $\text{1}\text{2}$ and spin I for the Breit-Rabi hamiltonian, the sum of contact hyperfine and Zeeman terms. We obtain the time dependence of the polarizations by solving the eigenvalue problems for the interaction hamiltonian and discuss some applications.     

Microscopic determination of nuclear deformation energy surfaces at very high spins

The deformation energy surfaces of a number of rare-earth nuclei are calculated microscopically as a function of the Bohr-Mottelson deformation parameters (β,γ), for the very high spin states $\text{(30}\text{h}\text{?}\text{?J?70}\text{h}\text{?}\text{)}$ and compared with semiphenomenological Strutinsky based calculations. The possibility of rotational isomers (yrast traps) is discussed.     

Bound state models for fermion Regge poles

Trajectories of fermion Regge poles are calculated in a model in which a spin $\text{1}\text{2}$ particle is bound to a spin 0 core. The leading trajectory with parity $\text{(?1)}{}^{\mathrm{<mtext>j?</mtext><mtext>1</mtext><mtext>2</mtext>}}$ is much like the boson trajectory generated by similar interactions. The opposite parity trajectory satisfies the constraints of MacDowell symmetry, yet is totally distinct for s>0. The model produces a trajectory which above the elastic threshold has a small negative Im α and an increasing Re α. Such a trajectory produces poles on the physical sheet of the energy plane.     

The parallel magnetic susceptibility and specific heat of the antiferromagnetic Ising linear-chain system with spin S = 2, 52, and 3

The parallel magnetic susceptibility and specific heat of the antiferromagnetic Ising linear-chain system with spin S = 2, $\text{5}\text{2}$, and 3 are calculated using the matrix approach. The results for spin $\text{S =}\text{1}\text{2}$, 1, $\text{3}\text{2}$, and 2 are checked against known results for these cases.     

Analyzing powers of valence and inner neutron-hole states in 115Sn via the 116Sn(d, t) reaction

The reaction ¹¹⁶Sn($\text{d}$, t)¹¹⁵Sn up to 7.5 MeV excitation energy has been studied at 40 MeV incident energy using a vector polarized deuteron beam. The measured analyzing power reveals strong J-dependence effects and has been used to clearly assign the spin of a number of low-lying states in the ¹¹⁵Sn nucleus. At higher excitation energy, a broad and fragmented bump is observed between 3.7 and 6.0 MeV in ¹¹⁵Sn. This work reports on one of the first attempts to determine the spin of such structure through polarization measurements. The analyzing power data indicates a mixing of spins $\text{J =}\text{9}\text{2}\text{,}\text{1}\text{2}$, in agreement with the excitation of the $\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{and}\text{2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ inner neutron-hole strengths in the ¹¹⁵Sn nucleus. In addition, some $\text{2}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ components are observed around ~ 4.6 MeV excitation energy.     

The nuclear structure of 239U

The γ-radiation resulting from capture of 2 keV, 24 keV and polarized thermal neutrons in enriched ²³⁸U has been investigated. All levels in ²³⁹U with $\text{J ≦}\text{5}\text{2}$ below 1.2 MeV have been identified with many unambiguous spin assignments resulting from the combined average resonance capture and circular polarization analysis. Seventeen previously unobserved states have been identified, six of them with $\text{J =}\text{5}\text{2}$.