H Walker, R D. Suenram, A C. Samuels, J O. Jensen, M W. Ellzy, J M. Lochner, D Zeroka
To demostrate the possibilities of using molecular-beam Fourier-transform microwave spectroscopy as a measurement technique to unambiguously detect and monitor chemical warfare agents, we report the first observation and assignment of the rotational spectrum of the nerve agent sarin (GB) [Methylphosphonofluoridic acid 1-methyl-ethyl ester, CAS #107-4408]. Only one conformer of this organophosphorus compound (C4H10FO2P) was observed in the cold (1 K) molecular beam. The experimental ground-state rotational constants of the observed conformer of sarin are A = 2874.0710(9) MHz, B = 1168.5776(4) MHz, C = 1056.3363(4) MHz (Type AStandard Uncertainties are given). Several of the 74 a-, b-, and c-type measured transitions are split into doublets resulting from the internal rotation of the methyl group attached to the phosphorus. The three-fold barrier to internal rotation determined from these splittings is 677.0 (4) cm-1, and the angle between the methyl top axis and the a-principal inertial axis is 62.70(4) . Ab initio calculations at the HF, DFT and MP2 levels of theory have also been carried out. Structures for two of the theoretical, low-energy conformers are presented and compared with experiment.
Journal of Molecular Spectroscopy
chemical warfare agent, detection, microwave spectroscopy, rotational spectrum, sarin
, Suenram, R.
, Samuels, A.
, Jensen, J.
, Ellzy, M.
, Lochner, J.
and Zeroka, D.
Rotational Spectrum of Sarin, Journal of Molecular Spectroscopy
(Accessed June 10, 2023)