A vibronic analysis of the electronic transition in thiophosgene

The ultraviolet absorption spectrum assigned to the electronic transition has been photographed under conditions of moderately high resolution. The spectrum proved to be very complicated and only 30% of the observed bands could be assigned. Three progressions were located in the spectrum and were assigned to ν″₄, ν′₄, and ν′₁. Inversion doubling splittings were obtained for a number of cold bands from an analysis of the hot bands in ν″₄. The inversion doubling splittings were sensitive to ν₁ and ν₄. An estimate was made for the barrier to inversion along each of these directions.     

Quantitative laboratory spectra and spectral line parameters for the v2 and v4 bands of PH3 applicable to spectral radiative models of the atmosphere of Jupiter

Quantitative laboratory PH₃ absorption spectra were obtained in the 800–1350 cm^-1 region, at ～0.05 cm^-1 resolution, with gas amounts corresponding to observed PH₃ absorptions in the atmosphere of Jupiter. A compilation of spectral line positions, intensities and ground state energies has been generated for the v₂ and v₄ bands of PH₃. Line-by-line calculations have been compared with the experimental spectra.     

The Forbidden RotationalQ-Branch of CH3CF3: Torsional Properties and (A1−A2) Splittings

The pure rotational spectrum driven by the small distortion dipole moment perpendicular to the symmetry axis has been investigated between 8 and 18 GHz for CH₃CF₃in the ground vibrational state using a pulsed Fourier transform waveguide spectrometer. This molecule has been selected as a prototype for the case of a symmetric top with small (∼500 kHz) torsional energy splittings in the ground torsional state (ν₆= 0). In this state, six (k± 3 ←k)Q-branch series have been measured for lower stateK= |k| between 3 and 8 with 27 ≤J≤ 75. For (ν₆= 1), three series with lower stateKbetween 5 and 7 with 49 ≤J≤ 66 have been observed. In two of these series, the torsional fine structure extending over ∼6.8 MHz has been fully resolved. The (A₁−A₂) splitting has been measured in the (ν₆= 0) series (K= 6 ← 3) for 37 ≤J≤ 74. The global data set of 443 frequencies included avoided-crossing molecular-beam splittings of Meerts and Ozier (1991.Chem. Phys.152, 241–259) and mm-waveR-branch measurements of Bocquetet al.(1994.J. Mol. Spectrosc.165, 494–499). In a weighted least-squares analysis, a good fit was obtained by varying 18 parameters in a Hamiltonian that represented both the torsional effects and the sextic splittings. Effective values have been determined for both rotational constants, eight torsional parameters including the barrier height, six diagonal centrifugal distortion constants, and two centrifugal distortion constants (? and ?_J) that characterize the (Δk= ±3) matrix elements. The difficulties are discussed that arise in defining a unique model for the torsional terms in the Hamiltonian when a high barrier symmetric top is investigated by distortion moment spectroscopy. The redundancies are investigated that exist in the quartic and sextic Hamiltonian for a near-spherical top such as CH₃CF₃.     

Absorptionsspektren von Er3+ in InCl3 und in ScCl3

The optical absorption spectra of Er³⁺ in single crystals of InCl₃ and ScCl₃ have been obtained between 14,000 and 29,000 cm^?1. The observed crystal field splittings are interpreted in terms of crystal potential of symmetry 3m for ScCl₃ and of symmetry 2m for InCl₃. There is however found, that for both cases the splittings will be approximately explained by a crystal potential of cubic symmetry. The employed hostlattices are of special interest, because the ions of the iron series can occupy the same sites as the rare earth ions.     

H2-broadening,shifting and mixing coefficients of the doublets in the ν2 and ν4 bands of PH3 at room temperature

The broadening, shifting and mixing coefficients of the doublet spectral lines in the ν₂ and ν₄ bands of PH₃ perturbed by H₂ have been determined at room temperature. Indeed, the collisional spectroscopic parameters: intensities, line widths, line shifts and line mixing parameters, are all grouped together in the collisional relaxation matrix. To analyse the collisional process and physical effects on spectra of phosphine (PH₃), we have used the measurements carried out using a tunable diode-laser spectrometer in the ν₂ and ν₄ bands of PH₃ perturbed by hydrogen (H₂) at room temperature. The recorded spectra are fitted by the Voigt profile and the speed-dependent uncorrelated hard collision model of Rautian and Sobelman. These profiles are developed in the studies of isolated lines and are modified to account for the line mixing effects in the overlapping lines. The line widths, line shifts and line mixing parameters are given for six A₁ and A₂ doublet lines with quantum numbers K = 3n,?(n = 1,?2, …) and overlapped by collisional broadening at pressures of less than 50 mbar.     

An INDO study of the hyperfine coupling constants and equilibrium geometries of some tetra-atomic radicals

Equilibrium geometries and isotropic hyperfine coupling constants have been estimated for the series of radicals CH _n F_3-n , CH _n Cl_3-n , CCl _n F_3-n and S₁H _n F_3-n using the INDO method. The theoretical hyperfine splittings agree well with experimental values including the unusually large proton splittings of 34·6 G and 89·9 G recently reported for SiH₂F and SiHF₂.     

Spectroscopic line parameters of NH3 and PH3 in the far infrared

NH₃ and PH₃ rotation and rotation-inversion line parameters in the far to medium i.r. are calculated for remote sounding purposes of planetary atmospheres; 1607 lines of ¹⁴NH₃, 362 lines of ¹⁵NH₃ and 325 lines of PH₃ are compiled. The absolute intensity formulation has been reviewed in the case of rotation adn rotation-inversion lines of molecules with C_3v symmetry. The justification of the general agreement between the authors, and comparisons with other published expressions are given.     

The anharmonic force fields of PH3, PHF2, PF3, PH5, and H3PO

The cubic and quartic force fields of the title compounds are determined from ab initio SCF calculations using 6-31G^** and TZP/TZ2P basis sets. The computed geometries, vibration-rotation interaction constants, l-doubling constants, anharmonicity constants, and vibrational wavenumbers are compared with the available experimental data, especially for PH₃ and PF₃. Many experimentally unknown spectroscopic constants are predicted. A scaling procedure based on calculated harmonic and anharmonic force fields is proposed for predicting the vibrational wavenumbers of unknown molecules such as PH₅.     

On the Determination of the Equilibrium Structure of the PH3 Molecule

Values of the r_e and α_e equilibrium structural parameters of the PH₃ molecule have been determined on the basis of experimental data on the fundamental bands of the PH₂D and PHD₂ species only, without any knowledge of the force-constant-type parameters of the PH₃ molecule. The functions of the equilibrium rotational parameters A^e, B^e, and C^e have been determined. These functions are totally independent of the values of any resonance interaction parameters. Then these functions have been used to determine r_e and α_e constants. The obtained values r_e=(1.416 776±0.000 164) Å and α_e=(93.56±0.29)° differ a little from those found in the earlier literature.     

Spectral studies of Nd3+ and Er3+ ions in POCl3:SnCl4 laser liquid

The optical absorption spectra of triply ionized neodymium and erbium ions in POCl₃SnCl₄ laser liquid have been studied for the first time in the UV-VIS and NIR regions. Spectroscopic and Judd-Ofelt intensity parameters are evaluated from the observed band positions and their intensities. Radiative lifetimes and the luminescent branching ratios for the excited fluorescent levels of Nd³⁺ and Er³⁺ ions are theoretically estimated and the possible laser transitions are indicated. From the observed splittings of certain bands in the second-derivative spectrum of the Nd³⁺ ion, the crystal field (A ₂₀,A ₄₀) parameters are evaluated assumingC _3h symmetry for the ion.     

Interaction of PH3 coadsorbed with H2, D2, O2 and H2O on Rh(100)

The coadsorption of PH₃ with H₂, D₂, O₂ and H₂O on Rh(100) has been studied using temperature programmed desorption (TPD), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). The adsorption and molecular desorption of PH₃ is not affected by preadsorbed H₂, D₂ and O₂. Preadsorbed PH₃ blocks H₂ desorption sites while postdosed PH₃ displaces H₂ (D₂₁) from the Rh(100). When D₂ and PH₃ are coadsorbed, no D appears in desorbed phosphine. Preadsorbed O₂ reduces the amount of H₂ desorption (from PH₃ decomposition) and increases the H₂ desorption temperature. There is also some reaction between O(a) and H(a) to form water. Preexposure to H₂O decreases the extent of PH₃ adsorption and of PH₃ decomposition.     

Raman and IR spectra of crystalline phosphine in the γ phase

The γ phase of crystalline phosphine has been studied using IR and Raman spectroscopy. The observations include both pure phases, PH₃ and PD₃, and many of the modes of PH₃, PH₂D and PHD₂ dilute in PD₃ as well as of PD₃, PD₂H and PDH₃ dilute in PH₃. The phase transition β → γ is very slow for PH₃, but much more rapid for PD₃.Evidence is adduced pointing to the existence of inequivalent sites in this crystal, but none of a number of suggested models for the unit cell is entirely consistent with the numbers of multiplet components of the internal modes, nor with the numbers of external (lattice) modes observed in the IR and Raman.     

A study of the K = 3nA1 - A2 centrifugal splitting in the 3ν2 and 4ν2 states of PH3 using a difference-frequency laser system

A frequency tunable infrared source has been constructed by using the (Ar-laser) - (dyelaser) difference frequency method developed by Pine and applied to the observation of the overtone bands of PH₃ 3ν₂ ← 0 and 4ν₂ ← ν₂ in the 3.4 μm region and 4ν₂ ← 0 in the 1.6-μm region. A Stark modulation method was used to increase the sensitivity of detection. For transitions which were well modulated, the minimum detectable absorption coefficient was estimated to be ～3 × 10^?7 cm^?1 using a 3-m cell. Emphasis was placed on the observation of the A₁-A₂ splitting for K = 3n rotational levels. For the 3ν₂ state splittings were observed for K = 3, 6, and 9 because PH₃ is a very nearly spherical top in this state. The magnitude and the J dependence of the observed K = 3n splittings have been analyzed by using a normal symmetric rotor Hamiltonian and a centrifugal distortion term of the form $\text{τ}{}_{\mathrm{xxxz}}\text{[(J}{}_{\mathrm{+}}{}^3\text{+ J}{}_{\mathrm{?}}{}^3\text{)J}{}_{\mathrm{z}}\text{+ J}{}_{\mathrm{z}}\text{(J}{}_{\mathrm{+}}{}^3\text{+ J}{}_{\mathrm{?}}{}^3\text{)]}\text{4}$.     

A Higher-Order Calculation of The SiH3 ESR Spectrum

The e.s.r. spectrum of the simple SiH₃ radical in a low temperature matrix was first reported by Gordy and coworkers¹. They concluded that the large ²⁹Si splitting of 266 gauss is due to the strong deviation from planarity of the radical. This deviation from the simple methyl radical, which is known to be essentially planar, can be qualitatively explained by the electronegativity difference between silicon and carbon as suggested by Pauling². Several other silyl radicals have since been reported³, all have ³ splittings relatively larger than the corresponding ¹³C analogs. Recently several workers questioned the interpretation of the ²⁹Si splittings on the geometry of simple silyl radicals^4,5. Recent evidence appears to show that the silyl radical is not as strongly pyramidal as previously supposed. Biddles and Hudson⁴ pointed out that the ²⁹Si splittings are negative due to a negative magnetic moment, but the proton splittings can be either negative for a quasi-planar structure or positive for a pyramidal geometry. Satisfactory interpretation of the ²⁹Si splitting can be obtained from the INDO calculation, provided the proton splittings are negative. The large ²⁹Si splittingin SiH₃ calls for treatment of second and higher-order effects of the e.s.r. parameters⁶. A full calculation of SiH₃ is reported below.     

Dipole properties of PH3, PF3, PF5, PCl3, SiCl4, GeCl4, and SnCl4

Experimental and theoretical photoabsorption cross sections combined with constraints provided by the Kuhn–Reiche–Thomas sum rule, the high-energy behaviour of the dipole oscillator strength density, static dipole polarisabilities, and molar refractivity data when available are used to construct dipole oscillator strength distributions for PH₃, PF₃, PF₅, PCl₃, SiCl₄, GeCl₄, and SnCl₄. The distributions are used to predict dipole sum rules S(k), mean excitation energies I(k), and van der Waals C₆ coefficients.     

Antiferromagnetic order and 4f-instability of CePb3

We have measured the static magnetic susceptibility of CePb₃ and LaPb₃ between 0.5 and 1,000 K and 1.5 and 900 K, respectively and the specific heat of CePb₃ between 1.5 and 40 K. The data show clearly an antiferromagnetic phase transition at 1.25 K. The order occurs in a doublet 4f groundstate whose entropy is removed only partially by long range order. There are strong indications for quadrupole-quadrupole interactions enhancing the ordering energy over that from spin spin interactions alone. The CEF splittings seem to depend on temperature. The 4f-instability in CePb₃ is quite weak.     

Rotational energy cluster formation in XY3 molecules: Excited vibrational states of BiH3 and SbH3

Previous theoretical work on energy cluster formation at high rotational excitation in the vibrational ground state of PH₃ [S.N. Yurchenko, W. Thiel, S. Patchkovskii, P. Jensen, Phys. Chem. Chem. Phys. 7 (2005) 573] is extended to BiH₃ and SbH₃. By means of variational calculations of the rotation–vibration energies based on ab initio potential energy surfaces, we analyze the rotational energy clustering of BiH₃ and SbH₃ at J  70 for a number of vibrational states. We show that BiH₃ and SbH₃, with their pronounced local mode behaviour, exhibit cluster formation already at moderate rotational excitation. In addition, owing to its quasi-spherical-top character, BiH₃ undergoes an imperfect bifurcation at high J. This gives rise to an energy cluster type not present in PH₃ and SbH₃. We present a semi-classical approach to the construction of the rotational energy surfaces for vibrationally excited states.     

Luminescence study of the optically active uranyl crystals: NaUO2(CH3COO)3

Luminescence spectra of NaUO₂(CH₃COO)₃ single crystals at 4.2 K have been investigated by means of site selective excitation technique, circularly polarized luminescence and time-resolved luminescence spectroscopy. It has been found that the splittings in the pure electronic and their vibronic transition lines are ascribed to the transitions from two different emitting sites.     

Microwave and Raman spectra,dipole moment,barrier to internal rotation,and vibrational assignment of silylphosphine-d2

The microwave spectra of SiH₃PD₂ have been recorded in the range 26.5–40.0 GHz. Both a- and c-type transitions were observed and assigned. The rigid rotor rotational constants were determined to be A = 37589.06 ± 0.11, B = 5315.70 ± 0.02, and C = 5258.70 ± 0.02 MHz. The barrier to internal rotation has been calculated from the A-E splittings to be 1512 ± 26 cal/mole. The dipole moment components of |μ_a| = 0.22 ± 0.01, |μ_c| = 0.56 ± 0.01, and |μ_t| = 0.60 ± 0.01 D were determined from the Stark effect. By using previously determined microwave data for SiH₃PH₂, several structural parameters have been calculated and their values are compared to similar ones in other compounds. The Raman (0–2500 cm^?1) spectra of gaseous, liquid, and solid SiH₃PH₂ and gaseous SiH₃PD₂ have been recorded and interpreted in detail on the basis of C_s molecular symmetry.     

Zero field splittings of Gd3+IN Nd2(SO4)3 · 8H2O and Sm2(SO4)3 · 8H2O crystals at 273 K

The electron paramagnetic resonance (EPR) of Nd₂(SO₄)₃ · 8H₂O and Sm₂(SO₄)₃ · 8H₂O doped with Gd³⁺ has been carried out at 273 K and the spin-Hamiltonian parameters are deduced. The zero field splittings have been computed and compared with those observed directly by Bogle and Symmons. It is found that the discrepancy in the zero field splittings. between computed and directly observed values falls within the range of linewidths of directly observed values.