Excited states of donor bound excitons and bound multiexciton complexes in silicon

The high resolution photoluminescence spectra reported here show new lines giving the first evidence of excited states of excitons bound to P donors in Si. These excited states are of crucial importance for a recently proposed theory of the bound multiexciton complexes which is based on a shell model. In addition several other new lines associated with the decay of the bound multiexciton complexes, which were predicted by the shell model theory, have been observed and their behaviour is found to be in argeement with the theory.     

Excited states of a bound polaron

The results of the calculations of energies of states 2S and 2P of a bound electron interacting weakly with optical phonon field are presented.     

Excited states of a bound polaron

Expressions for the energies of the 3s, 3p and 3d states of a polaron, bound to a positively charged impurity ion in a polar crystal through a Coulomb potential, are obtained in analytic forms using perturbation theory. The values of these energies are calculated in several polar crystals.     

Scattering processes involving bound excitons in highly excited ZnO

ZnO shows, under high excitations at low temperatures, two different extrinsic emission bands on the low energy side of bound exciton emission lines. The temperature dependence of one of these bands shows good agreement with theoretical predictions for a bound exciton-free electron scattering process. A comparison is made with results of other authors, where similar emission structures have been interpreted in terms of biexciton recombination.     

Uniaxial stress effects and excited states for multiple bound excitons

The theoretical model for multiple bound excitons (MBE) recently introduced by Dean et al¹ is used to discuss uniaxial stress effects in silicon. The fine structures observed in MBE spectra for SiC and Si are qualitatively strikingly similar. However, the interpretation of the strongest features in terms of a specific model for excited states suggested by Kirczenow² and Thewalt³ is not valid for SiC.     

Lifetimes of bound excitons in CdSe

Lifetime measurements have been made on bound excitons in CdSe, by using the time-correlated single photon counting and a cw mode-locked dye laser. The lifetimes of the T₂ (an exciton bound to a neutral donor) and I₁ (an exciton bound to be a neutral acceptor) bound excitons have been determined to be 0.50±0.05 and 0.80±0.05 ns, respectively. These values are in good agreement with those predicted by the model of Rashba and Gurgenishvili.     

Triplet bound excitons in copper-doped gallium phosphide

This review describes a particular class of neutral defect complexes in GaP, represented by the variety of Cu-related centres, which are observed to bind excitons in a spin-like singlet-triplet configuration. The reasons for this are discussed and two subgroups are defined. One of these consists of centres which bind holes in localized orbitally nondegenerate spin states, but give rise to highly structured optical spectra. The other group is characterized by featureless photoluminescence spectra in the mid-gap spectral region due to a tight binding of both the electron and hole in spin-like states. Both groups are well described with an essentially identical spin-Hamiltonian formalism, as detailed optically detected magnetic resonance measurements have revealed. The relation of this class of neutral defects in GaP to similar complexes in other semiconductors is discussed.     

Excited states of hypernuclei

A two-body model of a hypernucleus with realistic N potentials is used to calculate the energies of the excited states of the particle in heavy hypernuclei. The positions of the levels are investigated as functions of: a) the form of the N potential, b) the size of the core nucleus and the form of the nucleon density, and c) the mass number A.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 33–37, April, 1980.     

Resonant Raman studies of bound excitons in CdS

A new electronic resonant Raman effect in CdS is reported. Resonance enhancement at the I₁ and I₂ bound excitons is observed in differently doped (Cl, J, Li) samples. The energy, intensity dependency and Zeeman splitting suggest an electronic Raman effect associated with excited states of acceptor and donor bound excitons.     

Excited states of HCl

Ab initio CI calculations are presented for potential curves for the valence states of HCl, for the vertical electronic spectrum and for the potential curve for the B ¹Σ⁺ state. The valence ¹Π, ³Π and ³Σ⁺ states are found to be repulsive. Calculated vertical excitation energies are in good agreement with experiment. The B ¹Σ⁺ curve is predicted to have a double minimum.     

Optical absorption by neutral bound excitons

In this note we determine the oscillator strengths for the dipole absorption of neutral bound excitons in direct gap semiconductors, using our previously obtained 35-term Page and Fraser type wave function, and taking into account the detailed electronic structure as well as the electron-hole exchange interaction.The envelope part of the oscillator strengths varies considerably with the electron-hole mass ratio $\text{σ =}\text{m}{}^1{}_{\mathrm{e}}\text{m}{}^1{}_{\mathrm{h}}$, and is maximum for the (D⁰, X)- complex when σ = 0.4. For typical σ-values (σ? 0.1–0.2), . But when σ approaches zero, the overlapping of the electron and the hole envelope wave functions of the (A⁰,X)-complex decreases progressively so that the oscillator strength also decreases and tends to zero.In the case of zinc-blende materials (T_d) and positive spin-orbit coupling at $\text{k}\text{= 0}$, we confirm that the line strength for transitions to or from $\text{J =}\text{1}\text{2}\text{(Γ}{}_6\text{)}$ or $\text{J =}\text{5}\text{2}\text{(Γ}{}_7\text{+ Γ}{}_8\text{)}$ level of the (A⁰, X)-complex is equal to one quarter of the line strength to or from the $\text{J =}\text{3}\text{2}\text{(Γ}{}_8\text{)}$ level.In the case of CdS, where our computed values are only in qualitative agreement with the experimental values, we discuss the use of the phenomenological result of Rashba.     

Excited states in124Xe

The isomer shift in the optical transition Eu II 4f⁷(⁸S ₇ ^2/o )⁶p_3/2 ^(7/2,3/2)4?4f⁷ (⁸S ₇ ^2/o )5d⁹D ₄ ^o , λ=6O4.95 nm, has been measured between the isotope^152gEu(3^?) and its isomer^152mEu(0^?). From the valuev(^152gEu)–v(^152mEu)=736(10) MHz the deformation parameter of^152mEu has been estimated to be^152mβ?+0.25. This value is smaller than^152gβ as obtained from isotope shift measurements and the spectroscopic quadrupole moment. The influence of the shape difference on the decay of^152mEu is discussed.     

Excited states in 130Ba

Excited states of ¹³⁰Ba have been studied by means of in-beam γ-ray spectroscopy and electron-spectroscopy via the reaction ¹²⁰Sn(¹³C, 3n). Spin and parity assignments have been made for 28 new levels. A comparison with a cranking-model calculation shows that the negative-parity band based on the 5^? state is a two-quasiproton band.     

Excited states in126Ba

The K=3/2 ₁ ^T rotational band has been identified in⁹⁹Y with a band-head energy of 536 keV. This result is in contradiction with previously reported data, but is in agreement with predictions of the IBFM/PTQM model.     

Excited states in128Ba

A group of proton emitters of Au, Ir, Re, Ta has been identified by means of mass values derived from the experimental data. The proton drip line has been determined. It is shown that on the boundary of the proton stability the values of proton pairing energies increase by about 50% as compared with the isotone nuclei near the betastability line.     

Accurate binding energies of neutral bound excitons

The binding energies of the exciton-neutral donor complex (D⁰,X) and the exciton-neutral acceptor complex (A⁰,X) are calculated by means of the variational method, within the effective mass approximation and for all values of the electron-to-hole mass ratio $\text{σ=}\text{m}{}^1{}_{\mathrm{e}}\text{m}{}^1{}_{\mathrm{h}}$. The used 35-term trial wave function, similar to that introduced by Page and Fraser in the case of σ = 1 for the posittonium hydride PsH takes account for all the distances between the four particles. The results obtained confirm the stability of the two neutral complexes whatever the value of σ may be. They improve the binding energies formerly obtained by means of the variational method for different limited σ-regions.     

Systematics of bound excitons and bound multiexciton complexes for shallow donors in silicon

We report luminescence measurements of transitions involving bound multiple exciton complexes in Si:Sb and Si:As. The systematics of the donor systems Si:P, Si:As and Si:Sb are examined. We find that the splittings between the two observed series of lines are independent of complex number and donor type.     

The cubic splitting of acceptor bound excitons in Si

The cubic splittings of the J = 2 states for bound excitons in Si:B, Si:A$\text{l}$, and Si:Ga are computed in the ground state configuration for the first time. We find our calculations are in good agreement with experiments. Our results support the current hole-hole coupling model for interpreting the experimental spectra.