### Abstract

Microwave measurements were made on the rotational spectrum of 2-sulpholene using a modified Flygare-Balle pulsed beam Fourier transform spectrometer. Analysis and calculations provided information on the large amplitude ring puckering vibration of this system. Twelve and six rotational transitions were measured for the v=0 and v=1 states of the ring puckering vibration, respectively. The transitions for each vibrational state were fitted to a Watson's A reduced Hamiltonian including terms for quartic distortion yielding for v=0 the values B=2125.96(6), C=983.28(8), Δ_{JK}=0.664(4), Δ_{K}=-0.34(4) MHz, and for v=1 the values A=3995(26), B=2128.3(1), C=1984.6(1), Δ_{JK}=-0.8(1), Δ_{K}=- 32(6) MHz. Subsequently, ab initio calculations were performed at the self-consistent-field (SCF)/3-21G^{*}, MP2/ 6-31G ^{*}, and MP4/6-31G^{*} levels of theory to determine the barrier to inversion. The MP4/6-31G^{*} barrier was ΔE=116 cm^{-1}, and can be considered to be the most accurate barrier value calculated in this study. An ab initio potential energy curve was calculated at the SCF/3-21G^{*} level in terms of a single parameter (ω) describing the large amplitude motion of the ring puckering. Vibration-coordinate dependence of the effective reduced mass associated with this large amplitude motion and the resultant kinetic energy expression was determined. The solutions of a one-dimensional Schrödinger equation solved within this double well potential yield a separation between the v=0 and v=1 large amplitude motion vibrational states of 8 cm^{-1} when the effective reduced mass was assumed constant, and a separation of 9 cm ^{-1} when the effective reduced mass was expressed as a function of the ω coordinate. The v=0 and v=1 eigenfunctions for the SCF ring puckering potential were found to give vibrationally averaged rotational constants in good agreement with those obtained from the microwave spectrum.

Original language | English (US) |
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Pages (from-to) | 7305-7314 |

Number of pages | 10 |

Journal | The Journal of Chemical Physics |

Volume | 99 |

Issue number | 10 |

Publication status | Published - 1993 |

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### ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics

### Cite this

*The Journal of Chemical Physics*,

*99*(10), 7305-7314.