Characters of the irreducible nonequivalent loaded corepresentations of some point groups

We present tables of the characters of the irreducible nonequivalent loaded corepresentations of the point groups C₀, C₂, S₂, C_h, C₃, C₄, S₄, C_2v, C_2h, D₂ C₆, S₆, C_3h, C_3v, D₃, C_4h, C_4v, D₄, D_2d, C_6h C_6v, D_3d. D₆, D_3h, T, T_h, T_d O and O_h.Translated from Izvestiya VUZ. Fizika, Vol. 11, No. 11, pp. 23–34, November, 1968.     

Magnetic circular dichroism of Pr3+ ions in yttrium—Aluminium garnet crystals

The spectra of the absorption and magnetic circular dichroism in the praseodymium-yttrium garnet-aluminate Pr³⁺:YAG have been studied within the visible and near ultraviolet (UV) spectral range for temperature T = 90 K and 300 K. Analysis of the spectral and the temperature dependences of the magnetooptical and optical spectra has made it possible to identify the optical 4f → 4f transitions occurring between the Stark sublevels of the ¹ D ₂, ³ P ₀, and ³ H ₄ multiplets in Pr³⁺:YAG. It has been shown that in the MCD mechanism in Pr³⁺:YAG within the visible and UV spectral range for the absorption bands due to both forbidden 4f → 4f and allowed 4f → 5d transitions, a significant role is being played by the effect of quantum-mechanical “mixing” of the states of the three lowest-energy Stark singlets of the ground-state ³ H ₄ multiplet of the non-Kramers RE Pr³⁺ ion.     

Lande g-Factors of 7d1D2 and 8d1D2 States of Mercury

Lande g-factors of 5d¹⁰6s7d¹D₂(1.0155) and 5d¹⁰6s8d¹D₂(1.0285) atomic mercury levels have been determined using quantum beats method after electron pulse excitation.     

Dibaryon signals in the excitation functions of polarized πd scattering

Quantitative estimates of the role of the dibaryon resonances ¹D₂, ³F₃ and ¹G₄ in the πd channel are made. Exc functions for vector and tensor polarisations for πd → π$\text{d}$ are calculated for T^π < 650 MeV by admixing dibaryon resonances of conservative strength to the impulse approximation background. The reliability of the background amplitudes for θ ? 70° is checked by comparing with results from a Faddeev calculation.     

Features of dual fluorescence of 1, 2, 3, 4- tetrahydroisoquinoline

In polar and nonpolar solvents, tetrahydroisoquinoline emits S₂ (ππ¹) → S₀ and S₁ (ππ¹) → S₀ dual fluorescence and T₁ (ππ¹) → S₀ phosphorescence on S₂ (ππ¹) ← S₀ excitation. When excited by S₁ (ππ¹) ← S₀ the molecule yields S₁ (ππ¹) → S₀ fluorescence and T₁ (ππ¹) → S₀ phosphorescence in nonpolar solvent but only fluorescence in polar solvents. Probable participation of intermediate S₁ (nπ¹), T₁(nπ¹) states in intersystem crossing and internal conversion processes and its significance in interpreting the results are discussed.     

Study of Nd2+ absorption in x-irradiated CaF2, SrF2, BaF2 crystals

The absorption spectra of x-irradiated alkaline-earth fluoride (CaF₂, SrF₂, BaF₂) crystals doped with Nd³⁺ ions have been investigated. X-irradiation results in creating the absorption bands of inter-configuration 4fⁿ–4fⁿ⁻¹–5 d¹ transitions of Nd²⁺. The charge reduction of the neodymium by irradiation is not temperature-stable and the ions reoxidation (Nd²⁺ → Nd³⁺) occurs under heating to 570 K in CaF₂, 520 K in SrF₂ and 470 K in BaF₂.     

Stark-Effekt-Untersuchungen der Hyperfeinstruktur der 5s25d2D3/2- und 5s25d2D3/2-Terme im In I-Spektrum

The level-crossing technique with combined electric and magnetic fields was used to investigate the hyperfine structure of the 5s ²5d ² D _3/2- and 5s ²6d ² D _3/2-stedes of the In I-spectrum. From the shifts of the level-crossing signals due to the Stark effect of the electric field the Stark constantsβ of both states were deduced: 5s ²5d ² D _3/2: ¦β¦=0.33(3) Mc/(kV/cm)² 5s ²6d ² D _3/2: ¦β¦=6(1) Mc/(kV/cm)². By theoretical calculations with wave functions of the Coulomb approximation one can show, that the Stark effect in both states is mainly due to admixtures of the 5s ²6p- resp.5s ²7p-configuration.     

Stark-Effekt-Untersuchungen in der Hyperfeinstruktur der 3s 2 3d 2 D 5/2- und2 D 3/2-Terme des Al I-Spektrums

The resonance fluorescence of the transitions 3d ² D _5/2,3/2 3p ² P _3/2,1/2 in the Al I-spectrum was observed as a function of a magnetic field. Adding an electric field parallel to the magnetic field the shifts of level crossing signals caused by the Stark effect of the electric field were used to separate overlapping signals of the 3d ² D _5/2- and 3d ² D _3/2-states. The following values of the Stark parametersβ of both states and the hyperfine structure constantsA andB of the 3d ² D _3/2-states were deduced: 3d ² D _3/2∶ ¦A¦=99(1) Me/sec · g_J/0,8,B/A=?0,22(12), ¦β¦=0.45 (8) Mc/sec/(kV/cm)² · g_J,/0.8, A/β< 0 3d²D_5/2∶ ¦β¦=0.16 (4) Mc/sec/(kV/cm)² · g_J/1.2, A/β>0. Some qualitative aspects of interconfiguration mixing in the 3d²D-states are discussed.     

πNN Dynamics in pp → pp,pp →πd and πd →πd Processes Below 1 GeV

pp and πd scattering and pp →πd reaction processes at incident proton laboratory energies T _L ≤ 1 GeV are studied in the framework of πNN dynamics. For this purpose three-body calculations are performed with the πN interaction in the P ₁₁, P ₃₃, S ₁₁ and S ₃₁ states and NN forces in the ³ S ₁ -³ D ₁, ¹ S ₀, and ³ P ₂ states. In addition, the backward-going pion contribution at the πNΔ vertex, the πN-ρN coupling, the heavy-meson exchanges in the NN → NN driving term, and the effect of the off-shell structure in the πN-ρN P ₃₃ interaction are taken into account. Received March 28, 1994; revised July 29, 1994; accepted for publication August 31, 1994     

Photoionization cross-section measurements from the 2p, 3d and 3s excited states of lithium

The photoionization cross-sections from the 2p²P_{1/2, 3/2}, 3d²D_{3/2, 5/2} and 3s²S_1/2 excited states of lithium have been measured at different ionizing laser wavelengths, above the first ionization threshold. The experiments are performed by using a thermionic diode working in the space charge limited mode and the cross-sections are measured by employing the saturation technique. By changing the ionization photon energy, a smooth frequency dependence of the cross-sections has been observed for the 2p and 3d states. The cross-section from the 3s excited state has been measured at a single photon energy. The measured values of the photoionization cross are compared with the available data.     

Raman line positions in molecular hydrogen: H2, HD,HT, D2, DT,and T2

Spontaneous Raman spectroscopy is used to determine line positions of the six isotopomers of molecular hydrogen: H₂, HD, HT, D₂, DT, and T₂. State populations as low as 1.3 × 10⁸ are detected with the present experimental apparatus. This sensitivity makes possible measurement of the first overtone Q-branch line positions for H₂ and D₂ and of higher rotational transitions than previous investigations. The line positions for D₂, DT, and T₂ indicate that literature values for molecular parameters do not predict accurately line positions of transitions at J values above the observed transitions from which they were determined. The results for the six molecular isotopomers show that ab initio energy levels restricted to the adiabatic approximation do not yield line positions within the experimental uncertainty whereas recent nonadiabatic calculations reproduce the present observations. Reexamination of literature results at high energies indicates discrepancies between the theoretical calculations and experimental vibrational band origins for all vibrational levels in HT, DT, and T₂. No experimental measurements are currently available that test the accuracy of nonadiabatic ab initio rotational levels at high energies.     

The heat capacity of the layer compound tetrachlorobis (methylammonium) manganese—II (CH3NH3)2MnCl4, from 10 to 300k

The heat capacity of the layer compound, tetrachlorobis (methylammonium) manganese II, (CH₃NH₃)₂MnCl₄, has been measured over the range 10K <T<300K. In this region, two structural phase transitions have been observed previously by other techniques: one transition is from a monoclinic low temperature (MLT) phase to a tetragonal low temperature (TLT) phase, and the other is from TLT to an orthorhombic room temperature (ORT) phase. The present experiments have shown that the lower transition (MLT→TLT) occurs at T = 94.37±0.05K with ΔH_t = 727±5 J mol^?1 and ΔS_t = 7.76±0.05 J K^?1 mol^?1, and the upper transition (TLT→ORT) takes place at T = 257.02±0.07K with ΔH_t = 116±1J mol^?1 and ΔS_t = 0.451±0.004 J K^?1mol^?1. These results are discussed in the light of recent measurements on (CH₃NH₃)₂CdCl₄, and also with regard to a recent theoretical model of the structural phase transitions in compounds of this type.In addition to the structural phase transitions, (CH₃NH₃)₂MnCl₄ also undergoes magnetic ordering at T < 150K. The magnetic component to the heat capacity, as deduced from a corresponding states comparison of the heat capacity of the present compound with that of the Cd compound, is shown to be consistent with the behaviour expected for a quasi 2-dimensional Heisenberg antiferromagnet.     

Radiative lifetimes of 7d, 8d <Superscript>1</Superscript>D<Subscript>2</Subscript> excited states of Hg I

Radiative lifetimes of 7d, 8d ¹ D ₂ excited states of Hg I are measured using pulsed two-photon excitation from the ground [Xe]5d ¹⁰6s ^{2 1} S ₀ mercury state, detecting the decay of the laser-induced fluorescence. The results are compared with theoretical values, obtained by means of a Hartree-Fock single configuration method, taking into account electron configuration interaction. The radiative lifetime value dependence on the effective principal quantum number for the nd ¹ D ₂ series is analyzed and compared with the quantum defect dependence. Received 25 February 2000 and Received in final form 26 July 2000     

The pd → tπ+ reaction in an isobar model: Angular distributions

Various wave function effects are studied in the differential cross section for the pd → tπ⁺ reaction. These include both S- and D-waves for the deuteron and the triton as well as the production of p-wave and d-wave pions. For the triton a parametrized Faddeev wave function is employed and for the deuteron a wave function of Hulthén or McGee type. The two-body correlations considered are NΔ(⁵S₂, ^5D₂, ⁵P₃) and NN(¹D₂) which are found to be the most important partial waves in the pp → dπ⁺ reaction.     

Luminescence from the Pr 4f5d and S0 states in LiLaP4O12

The photoluminescence and excitation spectra of Pr³⁺ activated LiLaP₄O₁₂ has been investigated in the 10-300 K temperature region. At all temperatures, the luminescence consists of optical transitions emanating from both the Pr³⁺ 4f¹5d¹ and the ¹S₀ states. However, at low temperatures the emission spectrum is dominated by the intraconfiguration emission transitions emanating from the Pr³⁺¹S₀ state. With increasing temperature, there is an exchange of intensity between the two emitting states; emission transitions from the ¹S₀ state exhibit strong intensity quenching while the 4f¹5d¹→4f² emission transitions reveal intensity gain. These results are explained on the basis of thermal population of the 4f¹5d¹ state by the ¹S₀ state. The energy barrier of 0.05 eV (403 cm⁻¹) for the nonradiative process is determined from the temperature dependence of the ¹S₀ lifetime.     

Laser-enhanced ionization studies of the blue satellite band in the Ca−Ar system associated with the electric-quadrupole transition 4s 21 S 0→4s3d 1 D 2 of calcium

Summary The collision-assisted electric-quadrupole transition 4s ²¹ S ₀→4s3d ¹ D ₂ of calcium at 4575 ? has been observed using the laser-enhanced ionization technique for the first time. A blue satellite band due to the interaction of calcium 4s3d ¹ D ₂ state with argon¹ S ₀ has also been detected at 4527 ? which is shifted by 48 ? from the isolated atomic calcium line. The line broadening cross-section for the blue satellite has been calculated by measuring its collisional broadening at various argon pressures. Important processes involved in the generation of this blue satellite band are qualitatively discussed. The authors of this paper have agreed to not receive the proofs for correction.     

Luminescence characteristics of the Pr3+ ion in SrAlF5

The paper reports on a study of luminescence and excitation spectra of SrAlF₅:Pr³⁺ (0.5 mol %) polycrystals performed at 10 and 300 K with synchrotron radiation in the range from 5 to 25 eV. The Pr³⁺ ions in SrAlF₅ were shown to emit successively two photons in transitions from the ¹ S ₀ and ³ P ₀ levels. The main energy characteristics of the compound, namely, the position of the 4f → 5d excitation band (5.95–8.0 eV), the energy separation between the ¹ S ₀, 4f and the lowest 5d levels (～0.15 eV), and the SrAlF₅ band gap width (～12 eV), were determined. SrAlF₅:Pr³⁺ was found to possess a number of features not found in other Pr³⁺-activated fluorides.     

He-H2(D2,T2)碰撞体系振转相互作用势及分波截面的理论计算

采用超分子单双迭代(包括非迭代三重激发)耦合簇理论CCSD(T)方法,选择由原子中心高斯函数和高斯键函数3s3p2d1f组成的大基组,计算了He-H₂(D₂,T₂)碰撞体系的H₂分子取不同键长时的相互作用势能面.运用Tang-Toennies势模型和非线性最小二乘法拟合构造了He与同位素分子H₂(D₂,T₂)在质心坐标系下的振转相互作用势.通过密耦计算得 关键词： 高斯键函数 Tang-Toennies势函数 分波截面 碰撞参数     

Polarisationseffekte in der Hyperfeinstruktur von65Cu I, 3d 94s 2 m 2 D

The hyperfinestructure of the transition⁶⁵CuI, 3d ¹⁰4p ² P _3/2—3d ⁹4s ² m ² D _5/2 was investigated by optical interferometric methods. For the hfs-factors the following values were found:A(⁶⁵Cu,m ² D _5/2)=26,79(3) mK andB(⁶⁵Cu,m ² D _5/2)=5,81(10) mK. The core polarization of them ² D-terms and the Sternheimer corrections in the calculation of the quadrupolmoment of copper 65 from theB-factors of the terms 3d ⁹ 4s² m ² D and 3d ¹⁰ 4p ² P _3/2. were discussed.