L. Cludi

The millimeter and submillimeter-wave spectrum of boron monofluoride: Equilibrium structure

Abstract Utilizing a dc discharge absorption cell the millimeter and submillimeter-wave spectra of 11BF and 10BF have been observed in the v = 0, 1, 2 and v = 0, 1 vibrational states, respectively. The Dunham constants of the two isotopomers and the boron electric nuclear quadrupole coupling constant as well as the spin-rotation interaction constant of boron and fluorine have been determined. By removing from the Y01 Dunham constant the contributions due to the breakdown of the Born-Oppenheimer approximation, the resulting equilibrium bond distance is r e = 1.262672(7) A .

Microwave, High-Resolution Infrared, and Quantum Chemical Investigations of CHBrF2: Ground and v4 = 1 States

A combined microwave, infrared, and computational investigation of CHBrF(2) is reported. For the vibrational ground state, measurements in the millimeter- and sub-millimeter-wave regions for CH(79)BrF(2) and CH(81)BrF(2) provided rotational and centrifugal-distortion constants up to the sextic terms as well as the hyperfine parameters (quadrupole-coupling and spin-rotation interaction constants) of the bromine nucleus. The determination of the latter was made possible by recording of spectra at sub-Doppler resolution, achieved by means of the Lamb-dip technique, and supporting the spectra analysis by high-level quantum chemical calculations at the coupled-cluster level. In this context, the importance of relativistic effects, which are of the order of 6.5% and included in the present work using second-order direct perturbation theory, needs to be emphasized for accurate predictions of the bromine quadrupole-coupling constants. The infrared measurements focused on the ν(4) fundamental band of CH(79)BrF(2). Fourier transform investigations using a synchrotron radiation source provided the necessary resolution for the observation and analysis of the rotational structure. The spectroscopic parameters of the v(4) = 1 state were found to be close to those of the vibrational ground state, indicating that the ν(4) band is essentially unaffected by perturbations.

Self‐collisional coupling and broadening in the asymmetric rotor CHF2Cl

The line shape of 15 selected CHF2Cl rotational transitions is studied in the 59–1049 GHz frequency region. Collisional broadening parameters are measured and compared to semiclassical calculations. For some pairs of lines a large collisional coupling effect is observed and analyzed. A semiclassical theoretical model is presented allowing calculations of the coupling parameters in good agreement with measurements.

Lamb-dip millimeter-wave spectrum, structure and dipole moment of HCCCCF

The ground state rotational spectrum of HCCCCF has been observed in the millimeter-wave region using the Lamb-dip technique and very accurate values of the spectroscopic constants have been obtained. Moreover, the observation of the ground state rotational spectra of the four 13C monosubstituted isotopomers and of the deuterated species of fluorodiacetylene have enabled the determination of the r0 and rs molecular structures. The electric dipole moment of HCCCCF has been determined by observing the Stark spectrum of the J=3�2 rotational transition. The equilibrium geometry and the dipole moment have been evaluated using different abinitio methods and comparison between experimental and theoretical results has been made.

Rotational spectra of CF+ and

Context. The astrophysical relevance of the fluoromethylidynium ion and its importance for the interstellar chemistry of fluorine motivated the present laboratory spectroscopic investigation of both 12 CF + and the corresponding 13 C-containing isotopologue, 13 CF + . Aims. This investigation has been carried out to provide accurate rest frequencies for future (radioastronomical) observations, to improve the accuracy of the values for the spectroscopic parameters available in the literature for CF + , and to provide them for the first time for 13 CF + . Methods. Rotational spectra of CF + and 13 CF + were recorded in the millimeter- and submillimeter-wave frequency ranges. Their investigation was supplemented by high-level quantum-chemical computations using state-of-the-art coupled-cluster techniques. Results. We report the most accurate ground-state rotational parameters available so far for CF + and 13 CF + . Conclusions. The ground-state rotational parameters as well as the rest frequencies of 13 CF + will be useful for future observational purposes with the aim of improving the knowledge of fluorine interstellar chemistry.

^{\sf 13}

Abstract 1-Phosphapropyne has been produced in the gas phase by pyrolysis of a mixture of ethane and phosphorus trichloride. The ground state rotational spectra of the most abundant isotopomer and of the isotopic variants 13 CH 3 CP and CH 3 13 CP have been investigated in the millimeter and submillimeter wave regions obtaining very accurate values of the quartic centrifugal distortion constants D J and D JK and of the sextic distortion constants H JK and H KJ .

CF+: accurate rest frequencies and spectroscopic parameters

Abstract Absorption Lamb-dips have been observed for the first time in the far infrared region using an optically pumped FIR laser side band spectrometer with a Fabry-Perot cavity as an absorption cell. Examples of saturation dips are presented for rotational lines of OCS, CHF 2 Cl, and CH 3 Br in the 23-cm −1 region.

Accurate quartic and sextic centrifugal distortion constants of CH3CP

Abstract Measurements of N 2 - and O 2 -broadening of the rotational spectrum of CHF 2 Cl have been performed up to frequencies of 686 GHz. The pressure broadening coefficients of eight different ( J +1) 2, J −1 ← J 1, J −1 rotational transitions have been measured and compared with semiclassical calculations. The observed decrease of the magnitude of pressure-broadening coefficients for J > 28 has been explained by considering line coupling effects which occur when the transitions ( J +1) 2, J −1 ← J 1, J −1 completely overlap the ( J +1) 3, J −1 ← J 2, J −1 ones.

Lamb-dip absorption spectroscopy in the far infrared region using a laser sideband spectrometer

Abstract The microwave and far infrared rotational spectrum in the ground vibrational state of 14 NF 3 has been observed and analyzed up to J = 60. A tunable sideband spectrometer has been used in the FIR region. The resulting molecular constants are (in MHz) B 0 = 10 681.092679(39), D J = 14.61109(11) 10 −3 D JK = −22.77154(71) × 10 −3 , H J = 0.019529(95) × 10 −6 , H JJK = −0.09847(96) × 10 −6 , H KKJ = 0.1490(10) × 10 −6 , L JJK = −0.00072(12) × 10 −9 , and ( eQq ) N = −7.0854(18). The millimeter-wave spectrum of 15 NF 3 has also been observed and analyzed, providing the following values of the rotational constants: B 0 = 10 629.47940(23), D J = 14.3234(12) 10 −3 , D JK = −22.2093(33) 10 −3 .

Pressure broadening by oxygen and nitrogen of the rotational spectrum of CHF2Cl (HCFC-22) in the millimeter and submillimeter wave region

The electric dipole moment of CF3CH2F (HFC-134a) has been determined with a good accuracy by observing the second order ΔMJ = 0 Stark spectrum of the J = 50,5 ← 41,4 rotational transition. In addition, the equilibrium geometry and the dipole moment have been evaluated using highly accurate ab initio methods. By comparing the experimental [μa = 0.4909(14) D and μb = 2.0254(39) D] and theoretical [μa = 0.35(1) D and μb = 2.02(1) D] dipole moment components, a very good agreement has been found.