Microwave spectrum of HSiO in the X(2)A' ground electronic state

The rotational spectrum of the HSiO radical has been measured in the millimeter-and submillimeter-wave regions. The radical is produced in a d.c. glow discharge plasma of a gaseous mixture of SiH4 and N2O. Molecular constants including magnetic hyperfine interaction constants of the hydrogen nucleus are determined accurately from the observed frequencies of 111 a-type R-branch transitions. A portion of quadratic force constants are derived from the centrifugal distortion constants and the inertial defect, and they are used to determine the zero point average structure of HSIO; r(z)(Si-O) = 1.5326(2) Angstrom and alpha(z)(HSiO)= 116.8(1)degrees, where r(z)(Si-H) is assumed to be 1.5066 Angstrom. (C) 1997 Elsevier Science B.V.