G. Graner

A global treatment of the v9 = 1 and v10 = 2 vibrational levels of propyne

Abstract A global simultaneous study of the interacting levels v 9 = 1 and v 10 = 2 of propyne, H 3 Cue5f8Cue5fcCue5f8H, has been performed. In the analysis three kinds of data have been used: 1488 infrared transitions from the ν 9 band, 1156 energies from the v 10 = 2 state, and 217 submillimeter transitions in the v 9 = 1 and v 10 = 2 vibrational states. A new set of molecular parameters for the states v 9 = 1; v 10 = 2, l 10 = ±2 as well as the l (2,2) and Fermi elements was obtained. To understand changes in the rotational constants with excitation of the ν 10 mode, the quasi-symmetric top model was used.

Fourier transform and diode laser spectroscopy of the ν2 and ν5 bands of H3Si35Cl and H3Si37Cl near 950 cm−1

Abstract The gas-phase infrared spectra of H3Si35Cl [35] and H3Si37Cl [37] have been recorded in the ν2, ν5 region near 950 cm−1. The [35] species was investigated with Fourier transform (FT) and dispersive spectrometers, with resolutions of 0.05 and 0.02 cm−1, respectively, while the [37] species was studied with FT techniques at a resolution of 0.04 cm−1 and diode laser spectroscopy at Doppler-limited resolution. A total of 2312 and 1459 transitions were fitted with standard deviations of 4.4 and 1.7 × 10−3 cm−1 for [35] and [37], respectively. Both ν2, 948.0162(4) and 947.98178(14) and ν5, 950.6617(3) and 950.65566(17) cm−1 ([35] and [37]) modes are strongly coupled by Coriolis x, y resonance with ζ 2,5 y ⋍ 0.64 , and show a positive intensity perturbation. Consistent sets of molecular parameters have been determined independently for both [35] and [37] species.

The 2ν1 + ν4 band of carbon tetrafluoride

Abstract The 2 ν 1 + ν 4 band of 12 CF 4 at 2445 cm −1 has been remeasured with a 0.005-cm −1 resolution by means of a Fourier interferometer. The spectral region investigated here lies between P (70) and R (52). More than 500 line clusters have been assigned. From these a least-squares fit with an overall standard deviation of 0.001 cm −1 has led to seven significant constants.

The infrared spectrum of CD3CN around 5 μm: The fundamental band ν5 with perturbations

Abstract The Fourier transform spectrum of CD3CN from 2040 to 2350 cm−1 measured at a resolution of 0.0054 cm−1 has been analyzed. The spectral region includes six overlapping bands. Altogether about 4500 lines have been assigned in them. The previous part of this work (K. Pekkala et al., J. Mol. Spectrosc.139, 377–404 (1990)) gave results for the bands 2ν60, ν3 + ν6, 2ν3, and ν1. This paper presents a detailed analysis of the numerous perturbations in the ν5 band. In the analysis, the upper state of the ν5 band was linked to the coupled band system 2ν6, ν3 + ν6, 2ν3, and ν1 by the Coriolis resonances ν 5 2ν 3 and ν 5 2ν 6 , and by the Fermi resonance ν 5 ν 3 + ν 6 . In addition, there are a Coriolis resonance with the fundamental ν2 and seven Fermi resonances with ternary or higher combinations. The upper state experimental energies of ν5 were fitted using a model in which rotational states of 14 vibrations altogether were coupled by various rovibrational interactions. The standard deviation of the least-squares fit in the present work is near to 0.01 cm−1. In the spectrum the region of the fundamental band ν2 is very complicated. Lines were assigned only to one subband, K = 6.

Rotational structure near the local mode limit: The “2ν1” and “ν1 + ν4” bands of H370GeI and H374Ge79Br

Abstract The overtones of the Geue5f8H stretching vibration near 4150 cm−1 of the monoisotopic germyl halides H3 74Ge79Br and H3 70GeI have been studied with an effective resolution (FWHM) of 7 × 10−3 cm−1. The rovibrational analysis in the normal mode approach reveals strong local perturbations for the bromide which limit the SD of the fit of 1687 somewhat arbitrarily selected lines to 2.3 × 10−3 cm−1. On the other hand, 3734 transitions of H3 70GeI were fitted with a SD of 0.39 × 10−3 cm−1, which is almost the precision of the data, to a model involving a perpendicular component, ν0 = 4163.7324 cm−1, interacting by a weak Coriolis resonance with a parallel component, ν0 = 4161.7859 cm−1. Comparison of the vibrational and rotational parameters of the v(Geue5f8H) = 2 states, for both species, with those associated with the vibrational fundamentals, discloses that these v1 = 2 and v1 = v4 = 1 states behave almost as expected for the components of the (200) manifold in the local mode picture. Energy levels belonging to the (110) manifold have also been discerned in the iodide through a Coriolis-type interaction. Rovibrational parameters obtained from the overtone analysis, which is unprecedented for a symmetric top with three coupled M-H oscillators, are compared with predictions for the local mode limit.

How high-resolution FTS can help in assigning pumped laser lines and vice-versa

Using the example of propyne CH3-CCH, we show how the analysis of a high resolution FT spectrum can help in assigning farinfrared and mid-infrared optically pumped laser emissions. The coincidences with 10P(14) of CO2 is analyzed in detail. Conversely, we show that the knowledge of the laser lines pumped by 10R(16) of CO2 leads to new assignments in the FT spectrum.