High-resolution FTIR study of the ν1 + ν3 and 2ν3 + ν5 + ν6 rovibrational bands of methyl bromide

Pressure broadening coefficients of transitions in the ν5 band of methyl bromide from fitting to Voigt and Galatry line profiles

“…Not surprisingly, there is an extensive literature on its infrared spectrum [6][7][8][9][10][11][12]. Pressure broadening studies of its vibration rotation transitions have been undertaken previously.…”

Anharmonic resonances between thev1+v±16,v3+v±15+ 2v06andv3+v∓15+ 2v±26vibrational bands of CH379Br

“…These values are certainly quite good approximations for the W~55 coupling in both molecules, although several band centres involving high values of v have necessarily been obtained in low resolution. However, in methyl bromide, the problem is more complicated because of the existence of another resonance intermixed with the Fermi resonance between vl and 2v ~ In fact, Betrencourt et al [4] showed that the v~ band of CH3Br is linked to the close lying v3 + v{ ~ + v{ t parallel band by an anharmonic resonance with a coupling [5][6][7][8], which would make the model of interaction still more complicated; a force field model taking both W~55 and W356 anharmonic couplings into account has been set up by Schneider and Thiel [8].) In a previous publication [5], we studied the z = 3 case, where we considered, as a first step only the interaction between v~ + v3 and 2v3 + v~ 1 + v{ ~.…”

“…However, in methyl bromide, the problem is more complicated because of the existence of another resonance intermixed with the Fermi resonance between vl and 2v ~ In fact, Betrencourt et al [4] showed that the v~ band of CH3Br is linked to the close lying v3 + v{ ~ + v{ t parallel band by an anharmonic resonance with a coupling [5][6][7][8], which would make the model of interaction still more complicated; a force field model taking both W~55 and W356 anharmonic couplings into account has been set up by Schneider and Thiel [8].) In a previous publication [5], we studied the z = 3 case, where we considered, as a first step only the interaction between v~ + v3 and 2v3 + v~ 1 + v{ ~. Indeed, the separation of vl and 2v ~ is sufficiently large to allow the Fermi resonance effects to be ignored, to the extent that they will make only second order contributions to the upper state vibration and rotation parameters determined.…”