15min:

TONY MASIELLO, 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); ARTHUR MAKI, 15012 24th Ave. S.E., Mill Creek WA, 98012.

We have been engaged in the measurement and analysis of high-resolution infrared spectra of enriched samples of ¹¹BF₃. The Bruker IFS 120HR Fourier transform spectrometer at the Pacific Northwest National Laboratory (PNNL) facilities has been used to obtain measurements that range in resolution from 0.0015 to 0.0035 cm^-1 with pathlengths of up to 32 m. The fundamental infrared active transitions and many hot bands, overtones and combination bands have been investigated.

A multiple reflection White cell was used to identify a number of weak states not directly visible from the ground state. One of these states, 3 ₄, visible as the hot band 3 ₄ - 2 ₄, is involved in a strong Fermi resonance with the ₃ fundamental and was directly measured for the first time. A rotational perturbation was found to couple the 2 ₂ and ₁ + ₄ vibrations through a K =2, l =-1 interaction constant. The infrared inactive ₁ symmetric-stretching mode was characterized by two independent routes, one using the transitions (110⁰0⁰) - (000⁰0⁰), A₂'' - A₁' and (110⁰0⁰) - (100⁰0⁰), A₂'' - A₁', and the other using the transitions (001¹0⁰) - (000⁰0⁰), E' - A₁' and (001¹0⁰) - (100⁰0⁰), E' - A₁'. Since the rovibrational parameters for the ₁ state are not equilibrium parameters (not parameters from the bottom of the potential well), they are slightly different for ¹¹BF₃ and ¹⁰BF₃. Rovibrational constants will be presented for a number of combination/overtone states as well as the Hamiltonian used to derive them.