15min:

W. Y. FAN, Z. LIU AND P. B. DAVIES, Department of Chemistry, Uiversity of Cambridge, Cambridge CB2 1EW, UK.

Many fundamental and hot band absorption lines of ²⁸Si³⁵Cl⁺, ²⁸Si³⁷Cl⁺, ²⁹Si³⁵Cl⁺ and ³⁰Si³⁵Cl⁺ have been detected between 630 and 700 cm^-1 in a SiCl₄/He ac discharge using diode laser velocity modulation spectroscopy. The data have been fitted to give mass independent coefficients U_kl. The derived spectroscopic constants for ²⁸Si³⁵Cl⁺ include \omega_e=678.24316(18) cm^-1 and B_e=0.2870288(14) cm^-1. The equilibrium internuclear distance is r_e=1.9439105(46)Å. The equilibrium dissociation energy calculated from the expanded Dunham-Morse potential is D_e=49431(57)cm^-1.