MOLECULAR-BEAM SPECTRUM OF THE 3.3-MU-M NU-12-BAND OF BENZENE

The ν12 e1u fundamental band of C6H6 has been recorded under collisionless low-temperature (≈10 K) molecular-beam conditions using bolometric detection of molecules excited by a linearscan-controlled color-center laser referenced to a dual-wavelength polarization-stabilized He Ne laser. The sub-Doppler instrumental linewidth of ≈12 MHz (full width at half-maximum) permits resolution of nearly every transition. Improved spectroscopic constants are obtained in a fit yielding a standard deviation of ≈2 MHz, reflecting the measurement precision. A weak anharmonic or parallel z-Coriolis perturbation is observed in the Kl = -5 and -6 sublevels and is attributed to a closely resonant, lower-lying high-order combination level. © 1991.