A determination of zeeman parameters for NO2 in its ground state

Extensive measurements of magnetic dipole transitions in the gas phase E.P.R. spectrum of NO₂ in its [Xtilde] ² A ₁ state are reported. This type of transition was first identified by Burch, Tanttila and Mizushima. The data have been fitted simultaneously with measurements from the far infra-red laser magnetic resonance spectrum of NO₂ to determine the principal components of the electron spin g-tensor. The results are consistent with Curl's relationship between the components of the electron spin and spin-rotation tensors. It is necessary to include the effects of centrifugal distortion of the spin-rotation interaction and two parameters describing this interaction are determined in the course of the analysis. Some discussion of the origins of these parameters is included.     

Excitation of singly charged germanium ion from the ground state of GeI

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 53, No. 2, pp. 197–201, August, 1990.     

Compensation-induced optical transitions within the ground state of shallow donors in Ge and Si

An approximate formula for integral intensity of the compensation-induced parity-forbidden optical transition within the ground state of shallow donors in Ge and Si is derived in the limit of small compensations. The lineshapes for absorptions in Ge(Sb), Ge(P), Ge(As) and Si(As) are also calculated.     

Isotope shifts of the ground state of neon: Refining the measurement results

Abstract—It has been revealed that the published results of measurements of the isotope shift of the ground state of even neon isotopes contain systematic errors. The errors are caused by the use of erroneous data regarding the absolute values of specific mass shifts of excited states and by the measurement errors of the isotope shifts themselves for transitions to the ground state. The isotope shift of the 2p⁵4s[3/2]₁ → 2p⁶(¹S₀) transition has been measured to be 2305 ± 20 MHz, the absolute specific mass shift of the 3p[3/2]₂: (2_р9) level has been determined to be 647 ± 10 MHz, and the isotope shift of the ground state has been found to be–3156 ± 30 MHz.     

DLTS and PTIS of new donors in oxygen-doped germanium

Two new DLTS bands I and II have been observed in n-type germanium containing 10¹⁶ cm^-3 interstitial oxygen. The signature of II is: E_c?E_II = 0.031 eV, K = 4 × 10⁷ cm^?2s^?1; level I is about half as deep. In addision, the excitation spectrum of I is recorded by PTIS. It is composed of three hydrogenic donor series Ia, b, c with activation energies 17.25, 17.6 and 18.1 meV. The donors I and II are thought to correspond with the well known thermal oxygen donors. Energies for the latter were determined at 0.017 and 0.04 eV from Hall effect by Fuller and Doleiden. The possibility of double donors is examined, in analogy with the case of oxygen donors in silicon.     

The gallium-site donors germanium and silicon in gallium phosphide

The node in the Bloch part of the electron wave function expected for a Ga-site donor in GaP removes the usual valley-orbit splitting and associated chemical shift. However, the T₂ ground state can still show a small spin-valley splitting into Γ₈ and Γ₇ states, as previously verified for the Sn donor. We find that the optical properties of the Ge and Si donors deviate appreciably from this “normal” behaviour. The Ge donor is anomalously deep, E_D ～ 202 meV, yet binds an exciton by ～63 meV consistent with the Haynes rule for neutral donors in GaP. We find that this exciton possesses the large oscillator strength, f～3.5 × 10^-3, Zeeman and piezo-optical splittings characteristic of a Γ₆, 1s(A₁) ground state, like a P rather than Ga-site donor. However, f and the exciton localization energy are consistent with expectation for E_D ～ 200 meV, as measured from the lowest set of X conduction band minima, if we assume a symmetric A₁-like wave function. A possible explanation for this unexpected result is advanced. The much shallower Si donor, E_D～82 meV, binds an exciton by only ～ 14 meV, also consistent with the Haynes rule. By contrast, we find this Ga-site donor to be normal except that our Zeeman and piezo-optical results indicate an inverted spin-valley splitting, about 25% of that for the still shallower Sn donor. We also discuss the numerous low-lying excited states, some anomalous phonon replicas in the Ge and Si donor bound exciton spectra and the magneto-optical properties of a sharp line near 2.24 eV, attributed to the decay of excitons bound to (S)_p-(Ge)_p donor-acceptor associates.     

Far-infrared recombination radiation from impact-ionized donors in germanium

We studied the far-infrared emission spectrum resulting from recombination of an electron with an ionized impurity of As and Sb in germanium under impact ionization at liquid, helium temperatures. The emission peaks at the position corresponding to the transition from the 2p _± excited state to the ground state. This observation indicates that recombination occurs through the capture by the excited states of the donor impurity, which is consistent with the cascade trap model. The intensity of emission radiation is of the order of 10⁻⁷ watts for the excitation power of about one watt, which implies a dominant process of recombination to be accompanied by phonon emission.     

Muon state dynamics in germanium and silicon

We have carried out implanted positive muon studies on the molecular metal system d_n- (DMe-DCNQI)₂ Cu in order to understand better its novel magnetic properties. Examples of these salts at different levels of deuteration were studied. The fully deuterated ( d₈) salt shows a metal–insulator (MI) transition around 80 K and a magnetic transition around 7 K. The muon spin relaxation rate is enhanced below the MI transition, reflecting the localisation of spins along the Cu columns, however, the increase in muon spin relaxation rate occurs well above the metal–insulator (MI) transition and suggests a slowdown of the spin fluctuations around 120 K. At temperatures below 7 K a zero field precession signal was observed as a result of the 3D magnetic ordering of the Cu spins. For a muon site associated with the ring of the DCNQI molecule, the local field distribution was found to be consistent with the previously proposed magnetic structure. A sharp nuclear quadrupolar level crossing resonance (QLCR) was observed at 50 G which was assigned to resonance with the imine nitrogen on the DCNQI molecule. This revised version was published online in July 2006 with corrections to the Cover Date.     

Low-temperature intracenter relaxation times of shallow donors in germanium

The relaxation times of localized states of antimony donors in unstrained and strained germanium uniaxially compressed along the [111] crystallographic direction are measured at cryogenic temperatures. The measurements are carried out in a single-wavelength pump–probe setup using radiation from the Novosibirsk free electron laser (NovoFEL). The relaxation times in unstrained crystals depend on the temperature and excitation photon energy. Measurements in strained crystals are carried out under stress bar S > 300, in which case the ground-state wavefunction is formed by states belonging to a single valley in the germanium conduction band. It is shown that the application of uniaxial strain leads to an increase in the relaxation time, which is explained by a decrease in the number of relaxation channels.     

Saturation of ionization edge absorption by donors in germanium

A study of saturation of the absorption and photoconductivity of Sb and P donors in Ge for radiation of 90 m wavelength, i.e., of energy very closely above their ionization edges is presented at T=9.3 K. Under these conditions negligible heating by the excess radiation energy is expected, which provides a convenient opportunity to study the kinetics of photoionization and recombination. From these measurements we have determined the donor capture cross section of electrons at 9.3 K to be _c=(1.2±0.7)×10^–12cm^–2, and the relaxation time from the 2s to the ground state as ₂₁=(5.8±1.0)×10^–10s. The saturation intensity of the absorption coefficient is around three orders of magnitude higher than the saturation intensity of the photoconductivity. We explain the nonlinear photoconductivity by the Debye-Conwell dependence of the mobility on the number of photoionized donors and compensating acceptors.     

Knight shifts of metals in the liquid state

A single orthogonalized plane wave calculation has been made, to zero order in the pseudopotential, of the direct contact Knight shift for 30 liquid metals. The average deviation from experimental values is approximately 15%. Larger unexplained divergences occur for Cu and Hg. In addition it is shown that to zero order in the pseudopotential the factorΩP _F in the Knight shift describing the electron density at the nucleus is almost unaffected by thermal expansion.     

Temperature dependent properties of the condensed electron-hole state in germanium

The energy of the condensed electron-hole state in germanium shows a blue shift when the temperature is raised, and it does not depend on excitation intensity. From the temperature dependence of the luminiscence intensity an ‘activation energy’ of 2.3 meV is determined for the condensed phase-free exciton transition. All experimental details can be explained by a two phase model. The experiments cannot be interpreted by the radiative recombination of biexcitons.     

Identification of the Li ground state

The proton-stripping reaction from a ¹¹Be radioactive beam incident on a beryllium target demonstrates that only (7±3)% of the ⁹Li residues in the reaction are in coincidence with the 2.7 MeV γ-ray corresponding to the ⁹Li first excited state. This implies that the previously observed low-energy neutrons from the decay of the unbound nucleus ¹⁰Li represent a direct l=0 transition to the ⁹Li ground state. Consequently, neutron-unbound ¹⁰Li is proven to have the same parity inversion as occurs in the case of ¹¹Be with a  intruder state below the natural parity state.