Rotationally resolved spectroscopy of the ν8 band of cis-methyl nitrite

Reinvestigation of the microwave and new high resolution far-infrared spectra of cis-methyl nitrite, CH3ONO: Rotational study of the two first torsional states

“…It reproduced the 2164 assigned far-infrared lines of the v t = 0 ground torsional state of cis-methyl nitrite with an root-mean-square deviation (rms) of 0.00012 cm À1 (12 6 J 6 81 and K max a 6 48). The ground-state rotational and centrifugal distortion parameters obtained are presented in Table 1 together with the values obtained by Ghosh et al [8] in their microwave study, and by Goss et al [21] in their combined fit of microwave and infrared combination differences of the m 8 band. Our values are very close to those obtained by Goss et al [21] but the sextic constants (U J , U JK , U KJ , U K ) are needed in our present fit to reproduce the observed line positions, as the J values covered in our study is much higher.…”

“…The ground-state rotational and centrifugal distortion parameters obtained are presented in Table 1 together with the values obtained by Ghosh et al [8] in their microwave study, and by Goss et al [21] in their combined fit of microwave and infrared combination differences of the m 8 band. Our values are very close to those obtained by Goss et al [21] but the sextic constants (U J , U JK , U KJ , U K ) are needed in our present fit to reproduce the observed line positions, as the J values covered in our study is much higher. As a consequence, our values of the rotational and centrifugal distortion parameters are also slightly more precise than the previous ones.…”

“…In this table, the PAM values of the rotational constants obtained from the three codes used in the present work (i.e. from BELGI in the third column, from the Maki's code in the fourth column and from XIAM in the fifth column) are compared with the values determined previously in the literature (two last columns) [8,21]. It is however obvious that the ''global'' method used by the BELGI code which simultaneously fits both A and E lines for v t = 0 and 1 is very different from the ''local'' methods used by Ghosh et al [8] with the Woods code or used in XIAM which fits the A and E species of the ground torsional state v t = 0 only.…”

“…It is also a very different approach than fitting unsplit A and E transitions by a Watson type Hamiltonian, as performed using the Maki's code or as performed in Ref. [21]. The values of the rotational parameters from BELGI transformed into the principal axis system differ from the values determined by the Maki's code by about 12-50 MHz.…”

“…To our knowledge, the only high resolution study in the infrared spectral range which has been published so far to our knowledge concerns the m 8 NO stretching mode of the cis isomer located at 841 cm À1 [21].…”