Microwave Spectrum, Ringhyphen;Puckering Potential Function, and Dipole Moment of Methylenecyclobutane

摘要

The microwave spectra of methylenecyclobutane in the ground state and in the first six excited states of the ringhyphen;puckering vibration have been assigned. Theugr;thinsp;equals;thinsp;0state andugr;thinsp;equals;thinsp;1state are very close in energy and are strongly coupled giving rise to nonrigidhyphen;rotor spectra. Analysis shows the energy difference to be 33 592 MHz. This energy difference together with the vibrational dependence of the rotational constants gives the ringhyphen;puckering potential function to be7.65lpar;X4thinsp;minus;thinsp;9.15X2rpar;cmminus;1whereXis a reduced ringhyphen;puckering coordinate. This potential function contains a barrier to ring inversion of 160thinsp;plusmn;thinsp;40 cmminus;1. Theacomponent of the dipole moment is found to be 0.514 D in the ground state and to have the ringhyphen;puckering vibrational dependencemgr;athinsp;equals;thinsp;0.496thinsp;plus;thinsp;0.0051 lang;X2rang;ugr;ugr;(debye).