INVESTIGATION OF THE GROUND VIBRATIONAL-STATE STRUCTURE OF (HCL)-CL-35 TRIMER BASED ON THE RESOLVED K-SUBSTRUCTURE, J-SUBSTRUCTURE OF THE NU(5) VIBRATIONAL BAND

The high resolution rovibrational IR spectrum of the antisymmetric (HC l)-Cl-35 stretching nu(5) vibrational band in the ((HCl)-Cl-35)(3) iso topomer of the trimer has been measured with a tunable infrared diode laser supersonic jet spectrometer. One of the most prominent features of the spectrum is a series of strong lines each formed with P-p or (r )R transitions, with resolved K, J substructure developing between two adjacent P-p or (r)R heads. Analyzing the spectrum of ((HCl)-Cl-35)(3 ) as the perpendicular band of an oblate symmetric rovibrator, the fol lowing molecular parameters have been obtained: nu(0)-C'zeta = 2809.77 698(6) cm(-1), B'' = 6.80414(55) x 10(-2) cm(-1), B' = 6.85943(55) x 1 0(-2) cm(-1), C'-C'' = 2.737(78) x 10(-4) cm(-1), D-JK'' = -8.40(38) x 10(-7) cm(-1), D-JK' = -8.14(38) x 10(-7) cm(-1), D-J'' = 4.26(16) x 10(-7) cm(-1), D-J' = 4.16(16) x 10(-7) cm(-1), D-K'' = 4.32(22) x 10( -7) cm(-1), D-K' = 4.16(22) x 10(-7) cm(-1). A relationship among the centrifugal distortion constants establishes that the geometry of ((HC l)-Cl-35)(3) is consistent with a dynamically averaged planar ground v ibrational state. The centers of mass of the (HCl)-Cl-35 components ar e separated by 3.693(1) Angstrom in this structure. Ab initio methods were also used to estimate the splitting due to the tunneling motions between clockwise (cw) and counterclockwise (ccw) identical structures . Both theoretical and experimental evidence indicate that the (HCl)(3 ) complex has a planar equilibrium structure with no observable tunnel ing probability between the cw and ccw forms, thus the molecular symme try group of the complex is proposed to be C-3h(M).