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An experimental approach to the study of thermal transport in the diamond-anvil high pressure cell is described and the elements of the thermal diffusivity tensor of β-oxygen are reported to a pressure of 9 GPa. The anisotropy in the thermal conductivity is found to be opposite in sense to that in the velocity of acoustic waves. Results are interpreted in terms of a lattice dynamical model in which the strong interactions between an atom and its first-, second-, and third-nearest neighbors are treated in tensorial form with parameters evaluated directly from experiment. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The six independent elastic constants of β-oxygen have been measured over a pressure range extending from 6.0 to 9.5 GPa. Neither central forces between individual atoms, nor central forces augmented by the interactions between axial distributions of charge can give a reasonable account of the data. Force constant matrices were found which can account for the elastic data and the previously observed librational frequency. These matrices are based on general, short range forces with many-body interactions only among atoms contained in the same pair of molecules. Vibrational densities of states, distributions of individual-mode Grüneisen parameters, heat capacities, and the equation of state derived from the pressure dependence of the elastic moduli are presented. [ABSTRACT FROM AUTHOR]

Using a free-jet expansion which incorporates a heated nozzle, we have recorded the laser excitation spectrum of the 460 nm band system of NiCl2 at a rotational temperature of ∼40 K. 35Cl/37Cl isotope shifts were resolved which permit the assignment of progressions involving the symmetric stretching vibrational mode and identify a triplet splitting with spacings of 96 and 149 cm-1 which is believed to be due to spin–orbit coupling. Sequence bands involving the bending vibrational mode are also tentatively assigned. Only a small change in the symmetric stretching vibrational wave number is found between the electronic states involved in this transition (ν’1 =356 cm-1, ν″1 =360 cm-1). This result and the triplet splitting observed are discussed with respect to the possible electronic states involved and the assignment of this band system as either a Laporte forbidden g↔g transition involving the d orbitals on the Ni atom or an allowed u↔g charge transfer transition. [ABSTRACT FROM AUTHOR]

The 18 373 cm-1 band in the fluorescence excitation spectrum of jet-cooled CrO2F2 has been recorded with 0.007 cm-1 linewidth. The stronger lines have been assigned to a type c transition, consistent with a B1←A1 vibronic transition analogous to that in CrO2Cl2. Ground-state rotational constants, A″=0.148, B″=0.130, and C″=0.120 cm-1, agree well with electron diffraction predictions. The B1 excited state is significantly perturbed. Evidence includes (i) a decreasing fluorescence yield with increasing J′, such that signals were not observed for J′>3, (ii) the appearance of ‘‘extra’’ lines in the spectrum, leading to perturbing levels strongly mixed with levels of the B1 state, and (iii) anomalous effective rotational constants for the B1 state. [ABSTRACT FROM AUTHOR]

Rotational spectra of the excited a 1Δ state of NH and ND have been observed by far infrared laser magnetic resonance spectroscopy. For ND(a 1Δ) the spectroscopic constants are B0=264 750.263(30) MHz, D0=14.383 83(91) MHz, aN =109.63(22) MHz, aD =11.03(23) MHz, eqQ(N)=-4.0(15) MHz, gr=-0.000 86(10), and gL =1.000 506(17). For NH (a 1Δ), the constants are B0=493 043.182(95) MHz, D0=50.453 MHz (constrained in fit), aN =109.65(85) MHz, aH =70.9(14) MHz, eqQ(N)=-4.0 MHz (constrained in fit), gr =-0.001 58(6), and gL =1.001 03 (constrained in fit). Aspects of the electronic structure of the radical as revealed by the magnetic hyperfine constants are discussed in relation to those of chemically similar systems. The Zeeman parameters are interpreted in terms of mixing of the a 1Δ state with the c 1Π state. [ABSTRACT FROM AUTHOR]

Offers information on a spectroscopic study on the electronic state of carbon monoxide. Details of the Hamiltonian approach; Interpretation of data on the lambda-doubling spectrum of carbon monoxide.