Knowledge Bank

The high resolution infrared absorption spectra of van der Waals(vdw) complexes of $BF3$ with rare gases have been measured near the $BF3$ monomer $\nu 3$ band $(\nu 0=1453.98cm-1)$. The vdW complexes of $BF3$ with Ne, Ar, and Kr were effectively formed in a supersonic free Jet and the spectra were recorded by observing direct absorption of a tunable diode laser. The absorption lines of complexes were in the forest of the monomer band, however, the spectrum taken with the sample seeded in He helped to identify these lines out of monomer lines. The observed linewidths were in the range of 70 - 120 MHz mostly contributed by the instrumental and Doppler widths. Thus the lifetime of the vibrationally excited state is much longer than $10-9sec$. A preliminary analysis of the observed spectra has been done by using a symmetric top rigid rotor Hamiltonian. The complex bands are all red shifted from the monomer band by -.566, -1.767, and $-2.577cm-1$ for the complexes with Ne, Ar, and Kr, respectively. These shifts in the band origins show a good correlation with the polarizability of the rare gases.