Ground state parameters of BiH3 from infrared and millimeter-wave spectra: ground state and equilibrium structures

Unstable, short-lived BiH₃ has been synthesized and investigated by rotational spectroscopy in the range 158 (J=1-0) to 1280 GHz (J=8-7). Quadrupole and spin-rotation hyperfine structures (eQq=584.676(96) MHz), and the A₁A₂ splitting of the K=3 ground state level, have been resolved. By merging the pure rotational data with 1764 ground state combination differences obtained from the analysis of high resolution Fourier transform infrared spectra of the ν₁-ν₄ bands [J. Mol. Spectrosc. (2004) (in press)] spanning J and K values up to 16 and 14, respectively, with 0?ΔK?9, the ground state rotational and centrifugal distortion constants up to octic and sextic terms for reductions A and B, respectively, have been determined. Of the reductions of the ground state rovibrational Hamiltonian, reduction B including ε rather than h₃ as off-diagonal element is clearly favored. An experimental r₀ structure of the very-near spherical oblate symmetric top BiH₃, r(BiH)=178.82 pm and α(HBiH)=90.320°, has been deduced from the rotational constants B₀=2.64160172(18) and C₀=2.6010403(31) cm⁻¹. The derived experimental r_e structure, r_e(BiH)=177.834(50) pm and α_e(HBiH)=90.321(10)°, was determined. This is in excellent agreement with the most recent ab initio structure, r_e(BiH)=177.84 pm, and α_e(HBiH)=90.12°.     

Chemical Reactions in the Manufacture of Waveguides for Long Distance Optical Data Transmission

One of the modern high technologies which has advanced enormously in the last few years is glass fiber technology. This is used in the manufacture of glass fibers for lighting purposes and for the optical transfer of analog and digital data with a high transfer density. The technical demands made on the glass fibers required for data transfer, the optical waveguides, are extremely high and are already fulfilled to a large extent by industry. At present about four million kilometers of fiber, worth ca. 800 million DM are produced worldwide (10% in the Federal Republic of Germany). Numerous chemical processes take place during the manufacture of optical waveguides. However, in contrast both to the high and constantly growing demands on the quality and to the increasing production volume of such fibers, little is in fact known about the reactions involved. The present article will attempt to develop a picture of the multifarious reactions occurring in the course of this technical process on the basis of literature data and our own studies.     

The Ground State Spectroscopic Parameters and Equilibrium Structure of PD3

Infrared spectra of PD₃ have been measured in the 20-320 cm⁻¹ range and in the region of the ν₂/ν₄ and ν₁/ν₃ fundamental bands near 750 and 1690 cm⁻¹, respectively, with a resolution of ca. 0.0025 cm⁻¹. Furthermore, submillimeter-wave spectra covering the J=4-3, 13-12, and 14-13 clusters in the vibrational ground state were recorded. The observed ΔJ=+1 rotational lines were augmented by about 5500 ground state combination differences formed from transitions belonging to the fundamental bands. Of these, 1300 involved perturbation-allowed lines with ΔK≠0. These data and observations taken from the literature were appropriately weighted and fitted to 14 ground state molecular constants. The A and B reductions of the rotational Hamiltonian were found to be equivalent. Improved effective ground state and equilibrium structures were determined for both PH₃ and PD₃; the equilibrium structures, r_e (PH)=141.1607(83) pm and α_e (HPH)=93.4184(95)° and r_e (PD)=141.1785(57) pm and α_e (DPD)=93.4252(68)°, are in good agreement.     

High-Resolution Infrared Study of PHD2: The P-H Stretching Bands ν1 and 2ν1

For the first time the infrared spectrum of PHD₂ was recorded in the region of the PH stretching fundamental ν₁ at 2324.005 cm⁻¹ and the overtone 2ν₁ at 4563.634 cm⁻¹ with a resolution of 4.2×10⁻³ cm⁻¹ and 8.8×10⁻³ cm⁻¹, respectively. In the analyses about 1340 and 1020 transitions were assigned to the corresponding ν₁ and 2ν₁ bands, which provided 316 and 248 upper energies, respectively. Since both the bands are sufficiently isolated, a standard Watson-type Hamiltonian (A-reduction, I^r-representation) was employed. The obtained sets of spectroscopic parameters correlate very well both with each other, and with the corresponding parameters of the ground vibrational state.     

Joint Rotational Analysis of 16 Vibrational States of HDSe

High-resolution Fourier transform spectra of HD⁸⁰Se in the region of the ν₁+ν₃, 2ν₂+ν₃, 2ν₁+ν₂, 3ν₁, and ν₂+2ν₃ absorption bands, with centers located between 4000 and 5500 cm⁻¹, were recorded and rovibrationally analyzed. Energies of the (101), (021), (210), (300), and (012) states, together with those of the formerly reported (010), (100), (020), (001), (120), (110), (030), (011), (200), (002), and (003) states, were jointly used as input information in a “global fit” procedure. This fit provided 161 spectroscopic parameters which reproduce 3323 observed energies with accuracies close to experimental uncertainties. These parameters are compared with those predicted from H₂Se. Moreover, experimental band centers for HSeD are compared with those calculated theoretically.     

Rotation spectrum and infrared fundamental bands of 123SbD3. Determination of molecular geometry and ab initio calculations of spectroscopic parameters

The high resolution infrared spectrum of ¹²³SbD₃ has been recorded in the 20–350?cm^?1 range and in the regions of the ν₁, ν₃ and ν₂, ν₄ fundamental bands centred at 1350 and 600?cm^?1, respectively. Splitting of the K′′?=?3, 6 lines have been observed both in the rotation and ro-vibration spectra. A large number of ‘perturbation allowed‘ transitions with selection rules Δ(k??l) =?±?3,?±?6, and?±?9 have been identified in all fundamental bands. Accurate ground state molecular parameters have been determined by means of a simultaneous fit of the rotational transitions and about 12?000 ground state combination differences from the infrared bands. The A and B reductions of the rotational Hamiltonian provided almost equivalent results. The molecular parameters of the ν _i ?=?1 (i?=?1???4) states were obtained as a result of the simultaneous analysis of the ν₁ (A₁)/ν₃ (E) stretching and of the ν₂ (A₁)/ν₄ (E) bending dyads. In fact, the corresponding excited states are affected by strong perturbations due to rovibrational interactions of Coriolis and k-type that have been treated explicitly in the model adopted for the analysis. Improved effective ground state and equilibrium geometries were determined for the molecule and compared to those of ¹²³SbH₃. Ab initio calculations at the coupled cluster CCSD(T) level with an energy-consistent large-core pseudopotential and large basis sets were carried out to determine the equilibrium structure, the anharmonic force field, and the associated spectroscopic constants of ¹²³SbH₃ and ¹²³SbD₃. The theoretical results are in good agreement with the experimental data.     

Hochmolekulare Perchlorsiloxane

High-molecular Perchlorosiloxanes The reaction of SiCl₄ and O₂ in the gas phase does not lead spontaneously to the thermodynamically favored products SiO₂ and Cl₂. At temperatures of about 1300 K a lot of intermediates Si_nO_mCl_4n?2m can be isolated. Massspectrometric investigations show the formation of chlorosiloxanes with n = 2…65 and m/n = 0,5…1,7 and molar masses up to 7000 D. These compounds – even the high molecular ones – show typical molecular behaviour: they are solulable in unpolar solvents like hexane and can be sublimed congruently. No indications could be found between the structures of Si? O-frameworks in the siloxanes and solid SiO₂-modifications.     

High resolution study of the 6ν1 P-H stretching band of the PHD2 molecule

The high resolution spectrum of a phosphine gas mixture containing PHD₂ was recorded at room temperature in the 12 550-12 770 cm⁻¹ region. A high sensitivity laser photoacoustic spectrometer consisting of a longitudinal resonant cell coupled to a Ti:sapphire ring laser was employed. More than 600 transitions were assigned to the 6ν₁ overtone band of PHD₂ up to J^max=20, K_a^max=6. A Hamiltonian model developed up to the octic centrifugal distortion terms was used. Seven rotational and centrifugal distortion parameters were fitted, the other ones being fixed to their values linearly extrapolated from ν₁ and 2ν₁. The derived parameters reproduce the initial data within the experimental uncertainties. The isolated character of the P-H bond is confirmed.     

Analysis of the (0 0 v(3)), v(3) = 1, 2, 3 Vibrotational States of HDSe

High-resolution Fourier transform spectra of HDSe in the region of the 2nu(3) and 3nu(3) bands were recorded and analyzed for five different (M)Se isotopic HDSe species. Energies obtained from rovibrational analyses of the (002) and (003) states, together with those taken of the (001) state from an earlier study [O. N. Ulenov, G. A. Onopenko, N. E. Tyabaeva, H. Bürger, and W. Jerzembeck, J. Mol. Spectrosc. 198, 27-39 (1999)], were used as input information for a "Global Fit" procedure. This fit provided 34 spectroscopic parameters for the HD(80)Se species which reproduced rotational-vibrational transitions of the (001), (002), and (003) states within experimental accuracy. Corresponding analyses were performed for the other (M)Se (M = 82, 78, 77, and 76) species. Copyright 2000 Academic Press.