title: CO dimer: the infrared spectrum revisited.
abstract: A broad-band (2135-2200 cm(-1)) infrared spectrum of the CO dimer is recorded using a tunable quantum cascade laser to probe a supersonic jet expansion with an effective rotational temperature of about 2.5 K. Analysis of the spectrum reveals the first known levels of the excited state (vCO = 1) with A(+) symmetry and establishes that resonant vibrational splittings are small (<0.2 cm(-1)) for both the C-bonded and O-bonded dimer isomers. The spectrum extends over a surprisingly large range, with somewhat reduced intensity above 2150 cm(-1). A total of 28 new "stacks" of rotational levels having A(-) symmetry are assigned for vCO = 1 on the basis of combination differences, adding to the 8 stacks previously known, and extending up to 51 cm(-1) above the vCO = 1 origin. Assignments are given for the first 13 stacks of vCO = 1 in terms of the very low frequency geared bending intermolecular vibration.
authors: Department of Physics and Astronomy, University of Calgary , 2500 University Drive North West, Calgary, Alberta T2N 1N4, Canada.
authors: Mojtaba
authors: M
authors: Rezaei
authors: S
authors: S
authors: Sheybani-Deloui
authors: N
authors: N
authors: Moazzen-Ahmadi
authors: K H
authors: KH
authors: Michaelian
authors: A R W
authors: AR
authors: McKellar