Infrared spectra of AlF3 in solid argon

Three infrared absorptions are assigned to AlF₃ isolated in solid argon: ν₂ = 286.2 cm^?1, ν₃ = 909.4 cm^?1, and ν₄ = 276.9 cm^?1. The multiplet pattern previously reported near 950 cm^?1 is not present in carefully isolated AlF₃. Our spectra do not conclusively rule out a pyramidal structure for AlF₃; however, no infrared absorptions can be confidently assigned to ν₁, the symmetric stretch.     

The infrared spectrum of InCl3 in solid argon

We report the infrared spectrum of InCl₃ in solid argon. The observed spectrum is consistent with a planar D_3h structure for this molecule.     

Two-exciton transition in the antiferromagnetic KNiF3 and K2NiF4

For the sharp band located at 31,200 cm^?1 in the three dimensional antiferromagnetic KNiF₃, the dependence of the oscillator strength on the Ni ion concentration and the stress-induced linear dichroic spectrum are studied. The polarization dependence of the corresponding band in the two dimensional antiferromagnetic K₂NiF₄ is also measured. The weak structure located at 30,780 cm^?1 is assigned as two-exciton transition, and the band at 31,200 cm^t?1 as a two-exciton transition accompanied with a T_1u phonon.     

Infrared spectroscopic study of the reaction of H atoms with CF2 in argon and nitrogen matrices

The concurrent generation of CF₂ and of H atoms upon exposure of samples containing CF₂N₂ and either HI or H₂S isolated in an argon or a nitrogen matrix at 14 K to 2537-Å mercury-arc radiation leads to the appearance of prominent infrared absorptions of HCF₂, demonstrating that this species is the primary product of the H + CF₂ reaction. Infrared absorptions assigned to HCF₂, DCF₂, CF₂I, and CF₂S in previous studies on other reaction systems are confirmed in the experimental studies here reported.     

Emission and excitation spectra of CCl2 in solid argon

Studies of the CCl₂ excitation spectra in solid argon give values of 624 and 304 cm^?1 for the upper-state vibrational modes ν₁ and ν₂, respectively. The 000-000 band of the electronic transition occurs at 17 092 cm^?1. Vibrational relaxation in the upper state is fast compared with the 3.6 μsec emission lifetime, and only vibrationally relaxed emission is observed.     

Adiabatic potential energies for Na2 and K2

Adiabatic potential energies (Σ states) were calculated for the systems Na₂ and K₂. Wells followed by bumps were observed for the ³Σ_u excited states dissociating to Na(3s) + Na(3p) and K(4s) + K(4p). Double minima for the ¹Σ_u states dissociating to Na(3s) + Na(4s) and K(4s) + K(5s) are reported.     

Ultraviolet absorption spectra of Zn2 and Cd2 in solid argon and krypton at 10 K

Zinc and cadmium atoms have been condensed with argon and krypton at 10 K. The most intense absorption is due to the ${}^1\text{P}{}_1\text{←}{}^1\text{S}{}_0$ atomic transition, and a weak band is due to the ${}^3\text{P}{}_1\text{←}{}^1\text{S}{}_0$ atomic absorption. Structured absorptions at 252 and 254 nm in solid argon and krypton with vibrational spacings of 140-120 cm^?1 are due to the ${}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{←}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ transition of Zn₂. Similar 273 and 277 nm absorptions with 110-90 cm^?1 vibrational spacings are due to Cd₂ in solid argon and krypton, respectively.     

SO2 adsorption capacity of K2CO3-impregnated activated carbon as a function of K2CO3 content loaded by soaking and incipient wetness

The SO₂ adsorption capacity of K₂CO₃-impregnated activated carbons, prepared by soaking carbon in large volumes of K₂CO₃ in solution of various concentrations, varies linearly with respect to the loading of K₂CO₃ on the carbon up to about 12% K₂CO₃ by weight. Above 12%, the capacity for SO₂ levels out and then decreases. This suggests that at high loadings the K₂CO₃ either aggregates and/or blocks pores of the activated carbon. In contrast, the adsorption capacity of carbons prepared by repeatedly (maximum of three times total) loading K₂CO₃ via incipient wetness is much larger than that of the soaked samples, up to 70% more, when the loading of K₂CO₃ is greater than 12%. Static and dynamic adsorption, DSC, SEM, EDX and incipient wetness studies of the samples show that the impregnant aggregates but does not block carbon pores.     

Interactions of D2O with CO and CO2 molecules at cryogenic temperatures

On the basis of the matrix effect of secondary-ion mass spectrometry (SIMS), the intermolecular interactions between D₂O and hydrophobic molecules have been investigated at temperature of 15 K. The D⁺ yield is found to be enhanced markedly relative to the D₃O⁺ yield when the D₂O molecule forms a complex with the CO or CO₂ molecules on the surface. The CO molecules are incorporated in the inner pores of amorphous solid water and then cover the outermost surface facing to the vacuum, which is followed by the 3D-island growth on it. A similar result is obtained for the adsorption of the CO₂ molecule but the filling of the inner pores is not complete due to the lower mobility of the CO₂ molecule. The D₂O film grows on the CO₂ layer, but a pure D₂O film is hardly formed on the CO layer due to the occurrence of intermixing.     

Nonadiabatic superconductivity in K3C60 and Rb3C60

We discuss the validity of Migdal–Eliashberg theory applied to the superconductor fullerides K₃C₆₀ and Rb₃C₆₀. Recently, the relevant superconductor properties have been measured, like the isotope coefficient, the energy gap and critical temperatures for these compounds and compared with their optical properties. They all present a very disperse band of phonon frequencies, running from very small to very large energies, the latter being close to the Fermi edge. Therefore, these materials exceed the limit of validity of the adiabatic Migdal theorem, measured with a nonadiabatic parameter m=w₀/E_F, where w₀ is a characteristic phonon frequency and E_F=250 meV, the Fermi level. We examine previous theories incorporating vertex corrections into the Eliashberg equations to deal with such a situation. We compare these approaches by calculating the critical temperatures using a multimodal Eliashberg spectral function ²F(w) to study the contribution of the various phononic modes. We arrive at the conclusion that the optical modes, not the intramolecular ones, are among those which maximize T_c independently of including vertex corrections or not. This result goes in the direction to understand why doped fullerides A₃C₆₀ are superconductors.     

三态K2分子飞秒含时光电子能谱的理论研究

利用三态模型和含时波包法, 研究了K₂分子在强飞秒抽运-探测激光场中延时、脉宽以及抽运波长对光电子能谱和波包动力学过程的影响. 研究结果表明, 激光场强较弱或者脉宽较短都可能不发生Autler-Townes分裂, 光电子能谱呈现出单峰结构; 延时和抽运波长的改变影响能峰结构、位置和相对峰高; 对于不同的抽运波长, 波包的振动周期是相同的, 波包振荡幅度随脉宽增大而减小; 光电子能谱反映了波包动力学信息. 研究结果可以为实验上实现分子的光控制以及量子调控过程提供一定的参考, 并为进一步研究K₂分子的动力学性质提供有用的信息.     

Paramagnetic properties of several rare earth compounds with K3Ln2(NO3)9 structure

We present measurements of the paramagnetic susceptibilities of K₃Pr₂(NO₃)₉ and K₃Sm₂(NO₃)₉, cubic materials with rare earth sites having threefold rotational symmetry about (111). The rare earth environment resembles that of the Ln₂Mg₃(NO₃)₁₂·24H₂O materials, and the magnetic susceptibilities show similarities but also interesting differences with Pr₂Mg₃(NO₃)₁₂·24H₂O and Sm₂Mg₃(NO₃)₁₂·24H₂O. Paramagnetic resonance experiments in K₃La₂(NO₃)₉ doped with these and several heavier lanthanides are also described and compared with theory.     

Time behaviour of diffuse band emission in Na2 and K2

The C states of sodium and potassium dimers were excited with short laser pulses (about 500 ps) and time evolution of the diffuse bands in Na₂ (413–456 nm) and K₂ (550–583 nm) was observed in fluorescence. The measured decay times were interpreted as lifetimes of unidentified triplet states giving origin to the diffuse bands. Our results contradict the values reported before.     

Matrix isolation study of the vacuum-ultraviolet photolysis of HCCIF2 and of HCCl2F. Infrared spectra of the parent molecules and of the ClCF2 and FCCl2 free radicals

Studies of the vacuum-ultraviolet photolysis of HCClF₂ and of HCCl₂F isolated in argon and nitrogen matrices at 14°K have led to the infrared spectroscopic identification of the free radicals ClCF₂ and FCCl₂, respectively. Support for this identification has been obtained from studies of the vacuum-ultraviolet photolysis of DCClF₂, of DCCl₂F, and of H¹³CCl₂F, as well as from studies of halogen-atom abstraction from CClF₃ and from CCl₃F by sodium atoms in an argon matrix environment. The CCl bonds of FCCl₂, like those of CCl₃ and of HCCl₂, appear to be exceptionally strong. Gas-phase infrared spectral data are also reported for DCClF₂ and for DCCl₂F, not previously studied. Vibrational assignments are proposed for these two molecules, and data supporting the reassignment of one of the CF stretching fundamentals of HCClF₂ are presented.     

Raman spectra of K2CuF4

The crystal structure of K₂CuF₄ has been studied by means of Raman scattering. The structure is found to belong to the space group D_4h⁵ rather than D_4h¹⁷ of K₂NiF₄ between 2 and 800 K because of the distortion arising from the “orbital ordering effect”.     

Mössbauer study of magnetic ordering in K2FeF4

The sublattice magnetization of the quadratic-layer basal-plane antiferromagnet K₂FeF₄ has been studied by use of Mössbauer spectroscopy. A distribution of Néel temperatures with a width ～3 K is found at a mean T_N = 67.2±0.3 K. For 0.3 < T/T_N < 0.99 the sublattice magnetization is described by a power law with critical exponent β = 0.17±0.01.     

Infrared optical response of YBa2Cu3O7 and PrBa2Cu3O7 An ellipsometric study

Ellipsometry was used to study (110) and (001) oriented films of YBa₂Cu₃O₇ and PrBa₂Cu₃O₇ in the mid-and near-infrared spectral regions. Below a photon energy of 0.1 eV, the in-plane component of the dielectric tensor of YBa₂Cu₃O₇ is dominated by a Drude term with a squared plasma energy of (3.0 ± 0.3) eV². This “oscillator strength”, and the Lorentzian broadening energy of (0.104 ± 0.005) eV at room temperature, are confirmed by the changes induced in Pr-substituted material, and by low-temperature measurements in the near-infrared. The deviation from the Drude behavior observed above 0.1 eV is accounted for by a broad absorption band with an oscillator strength of (3.6 ± 0.1) eV² in YBa₂Cu₃O₇ which shifts to higher energies and takes over almost all of the oscillator strength of the Drude term when Y is substituted by Pr. The response to electric fields perpendicular to the planes is much weaker, with an upper bound of 0.63 eV² for the squared plasma energy. The in-plane loss function computed from the measured dielectric function follows the Drude-like lineshape, modified by the bound-state absorption band, down to the lowest energy reached in our measurements (0.058 eV).     

Metastable chaotic state in K2ZnCl4

The ³⁵Cl NQR frequencies of K₂ZnCl₄ have been measured close to the incommensurate-commensurate transition. A calculation of the temperature dependence of the soliton density n_s from the NQR data showed that in K₂ZnCl₄ close to T_c exists a metastable chaotic state.     

Infrared spectroscopy of OCS,SO2, O3 with a CO2 waveguide laser

Infrared spectroscopy of OCS, SO₂, and O₃ has been performed with a CO₂ waveguide laser. The spectra observed were analyzed with data available and assignments are proposed.     

Scintillation properties of K2LaCl5 with Ce doping

In this work we present the scintillation properties of K₂LaCl₅ doped with Ce³⁺ concentrations of 0, 0.1, 1 and 10%. Under X-ray excitation the crystals show the efficient Ce³⁺ (5d–4f) luminescence between 340 and 400 nm. Depending on the Ce concentration, the light yields vary between 24,000 and 50,000 photons/MeV (ph/MeV). Experiments with 662 KeV gamma ray excitation show light yields varying between 13,000 and 30,000 ph/MeV. For Ce luminescence a single exponential decay time of approximately 40 ns is expected. However, for K₂LaCl₅:10%Ce, the decay is not single exponential. As a function of the time t, it can be described by a 1/t^1.63 behaviour for large t. With a crystal of K₂LaCl₅:10%Ce we obtained an energy resolution of 5.1% for 662 KeV gamma ray excitation of ¹³⁷Cs.