Rotational Spectrum of Sarin

Published

May 1, 2001

Author(s)

H Walker, R D. Suenram, A C. Samuels, J O. Jensen, M W. Ellzy, J M. Lochner, D Zeroka

Abstract

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.

Citation

Journal of Molecular Spectroscopy

Volume

207

Issue

No. 1

Pub Type

Journals

Keywords

chemical warfare agent, detection, microwave spectroscopy, rotational spectrum, sarin

Citation

Walker, H. , Suenram, R. , Samuels, A. , Jensen, J. , Ellzy, M. , Lochner, J. and Zeroka, D. (2001), Rotational Spectrum of Sarin, Journal of Molecular Spectroscopy (Accessed September 19, 2025)