15min:

M. A. MARTIN AND A. PERRY, Department of Chemistry, Oregon State University, Corvallis, OR, 97332-4003, USA; T. MASIELLO, Department of Chemistry and Biochemstry, California State University, East Bay, Hayward, CA, 94542, USA; K. SCHWARTZ, Department of Chemistry, Oregon State University, Corvallis, OR, 97332-4003, USA; J. W. NIBLER, Department of Chemistry, Oregon State University, Corvallis, OR, 97332-4003, USA; A. WEBER, Optical Technology Division, National Institute of Standards and Technology,Gaithersburg, MD, 20899-8441, USA; A. MAKI, 15012 24th Ave., S.E., Mill Creek, WA, 98012, USA; T. A. BLAKE, Pacific Northwest National Laboratory, P.O. BOX 999, Mail Stop K8-88, Richland, WA,USA.

Infrared spectra of the ₁₄(e') 540 cm^-1 ~and ₁₈(a₂") 835 cm^-1 ~bands of bicyclo[1.1.1]pentane have been recorded at a resolution sufficient (0.0015 cm^-1) to resolve for the first time individual rovibrational lines. This report presents the ground state constants for this molecule determined from two of the ten infrared-active fundamental bands. The fitted transitions were judged to be free of perturbations of their upper state levels. A combined total of more than 6000 lines with J and K quantum numbers of the two bands ranging up to about 60 were fit with an obs-calc RMS deviation of 0.00021 cm^-1. ~The following principal constants (in units of cm^-1) of the rovibrational ground state were obtained: B₀ = 0.23994136(30), D_J = 5.9959(96)x10^-8, ~and D_JK = -1.5052(98)x10^-8. The band centers were found to be ₁₄ = 540.326397(19) cm^-1 ~and ₁₈ = 832.92902(3) cm^-1. The values in parentheses represent the uncertainties (2 standard deviations) in the last digits of the value of the constants. The results are compared with those obtained for [1.1.1]propellane and with those computed at the ab initio anharmonic level using the B3LYP density functional method with a cc-pVTZ basis set.