15min:

WEI LIN, WALLACE C. PRINGLE, STEWART E. NOVICK, Department of Chemistry, Wesleyan University, Middletown, CT 06459; THOMAS A. BLAKE, Pacific Northwest National Laboratory, P. O. Box 999, Mail Stop K8-88, Richland, WA 99352 (PNNL is operated for the US Department of Energy by the Battelle Memorial Institute under contract DE-AC05-76RLO 1830).

Using a pulsed jet Fourier transform microwave spectrometer we have recorded the rotational spectrum of the argon-tropolone van der Waals complex between 6 and 17 GHz. Eighty-six transitions were observed (29 a-type and 57 b-type) with J'' values ranging from 2 to 8 and maximum K_a'' and K_c'' values of 5 and 8, respectively. The transitions were fit with a Watson A-reduction Hamiltonian in a I^r representation using the SPFIT program. The fit ground state constants for argon-tropolone are A=1080.4365(3) MHz, B=883.4943(3) MHz, C=749.0571(2) MHz, _J=2.591(2) kHz, _JK=-3.32(1) kHz, _K=5.232(9) kHz, _J=0.944(1) kHz, _K=-0.028(8) kHz. The rms error for the transition set in the fit is 4 kHz. When included in the Hamiltonian, the tunneling - rotation interaction term, F(J_aJ_b+J_bJ_a), did not improve the quality of the fit: proton tunneling in the complex appears to be quenched. The argon coordinates in the principal axis system of tropolone monomer are a=0.43 Å, b=0.23 Å, and c=3.48 Å.