Anharmonic resonances between the upper rovibrational levels of the and infrared bands of CH₃³⁵Cl studied in a high-resolution FTIR spectrum from 4250 to 4600 cm^-1

Abstract

Anharmonic resonances between the upper rovibrational levels of the and infrared bands of CH 3 35 Cl studied in a high-resolution FTIR spectrum from 4250 to 4600 cm -1 , Anharmonic resonances between the upper rovibrationai levels of the v2 + v4 ~ 1, v2 + 3v~ 19 V 1 "]" V~ 1 + 1 3VK , V4 .1 + V~ 1, _+1v~ 1 + 3v~ l, vs + 3v~ 3 and 2v3 + 3v6 ~1 infrared bands of CH33SCl studied in a high-resolution FTIR spectrum from 4250 to 4600 cm-1 82 K AK sub-bands, belonging to the eight vibrational bands of monoisotopic CH3ascI that are quoted in the title, have been identified. An r.m.s. standard deviation of 0-051 cm-1 has been achieved by a least-squares fit of 79 Q-branch head wavenumbers. For this purpose, a simplified model, taking into account anharmonic resonances between (i) v 2 + v~ t and v 2 + 3v6" t, (ii) v~ 1 + vs ~1 and vs ~1 + 3v21, (iii) v 2 + v~ t and v I + v~ =1, (iv) v 1 + v~ t and 3v~ 1, (v) v 1 + vs ~1 and v2 t + vs ~1 and (vi) v~ 1 + v~ 1 and vs ~t + 3v2 3, was used. For two of the three sub-bands not considered in the calculation, the difference between observed and calculated wavenumbers is small (0.2 cm-1); for the last one, it is much larger (1-18 cm-1), and this is probably caused by the upper level of 2v 3 + 3v~ 1, which has not been taken into account in the present model, because of the lack of information related to this band. t Permanent address: D6partement de Physique, Facult6 des Sciences, Universit6 Ibn Tofa'd, BP 133, Kenitra, Morocco. ~/Laboratoire associ6/t rUniversit6 Paris-Sud.