OBSERVATION OF STRONG HIDDEN LINES IN THE INFRARED-SPECTRUM OF THE CO-HE COMPLEX

In the only previous observation of spectra of the weakly bound comple x GO-He [C. E. Chuaqui, R. J. Le Roy, and A. R. W. McKellar, J. Chem. Phys. 101, 39 (1994)], only 6 out of the 21 strongest transitions were observed, and much of the analysis therefore relied on relatively wea k transitions. These strong ''hidden'' transitions are located very cl ose to, and were obscured by, pressure-broadened transitions of the CO monomer. In the present paper, the measurement of all but one of the 15 hidden transitions has been achieved by using a sensitive tunable d iode laser probe which allows much lower sample pressures. The results fully confirm the previous analysis, and provide additional precise d ata on the bound energy levels of this fundamental molecular system, e specially for the CO-He-3 isotope. (C) 1996 American Institute of Phys ics.