The aim of this work is the study of the spectrum of propyne ( CH3CCH ) in the range 6200-6700 cm-1. Several spectra have been recorded both at room and cryogenic temperatures. The band has been recorded at room temperature using a BOMEM DA3.002 Fourier transform spectrometer with an instrumental resolution of 0.004 cm1 achieving a resolution of 0.018 cm1, very near to the Doppler limit. Spectra have also been recorded using cavity ring down spectroscopy to probe a supersonic expansion of propyne seeded in Ar (Trot ≈ 20 K) under sub-Doppler conditions, achieving about 720 m effective absorption path length. In the investigated range, 4 parallel bands ( , , , ) and 1 perpendicular band ( ) have been identified and assigned. All the bands are perturbed by a complex system of vibro-rotational and anharmonic interactions. The spectrum at room temperature appears very congested owing to the presence of a large number of hot bands. In addition, most of the transitions are overlapped due to the large Doppler width of the lines. Low temperature spectra eliminate the hot bands and reduce the K structure of the bands and the width of the lines, facilitating the analysis. In total 1019 ro-vibration transitions have been identified and assigned. They have been fitted simultaneously to a model Hamiltonian which includes all symmetry allowed interactions between and within the excited state levels in order to obtain accurate values of the spectroscopic parameters. A tolerance limit of 0.005 cm1 has been used in the fitting procedure achieving a standard deviation in the final fit of 0.0019 cm1. A set of effective parameters has been determined since it has not been possible to take into account interactions with nearby states which have not been identified in the spectrum.
THE INFRARED SPECTRUM OF PROPYNE FROM 6200 TO 6700 CM-1
VILLA, MATTIA;FUSINA, LUCIANO;NIVELLINI, GIAN DOMENICO;
2011
Abstract
The aim of this work is the study of the spectrum of propyne ( CH3CCH ) in the range 6200-6700 cm-1. Several spectra have been recorded both at room and cryogenic temperatures. The band has been recorded at room temperature using a BOMEM DA3.002 Fourier transform spectrometer with an instrumental resolution of 0.004 cm1 achieving a resolution of 0.018 cm1, very near to the Doppler limit. Spectra have also been recorded using cavity ring down spectroscopy to probe a supersonic expansion of propyne seeded in Ar (Trot ≈ 20 K) under sub-Doppler conditions, achieving about 720 m effective absorption path length. In the investigated range, 4 parallel bands ( , , , ) and 1 perpendicular band ( ) have been identified and assigned. All the bands are perturbed by a complex system of vibro-rotational and anharmonic interactions. The spectrum at room temperature appears very congested owing to the presence of a large number of hot bands. In addition, most of the transitions are overlapped due to the large Doppler width of the lines. Low temperature spectra eliminate the hot bands and reduce the K structure of the bands and the width of the lines, facilitating the analysis. In total 1019 ro-vibration transitions have been identified and assigned. They have been fitted simultaneously to a model Hamiltonian which includes all symmetry allowed interactions between and within the excited state levels in order to obtain accurate values of the spectroscopic parameters. A tolerance limit of 0.005 cm1 has been used in the fitting procedure achieving a standard deviation in the final fit of 0.0019 cm1. A set of effective parameters has been determined since it has not been possible to take into account interactions with nearby states which have not been identified in the spectrum.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
