A New Look at the Infrared Spectrum of the Weakly Bound CO–N₂ Complex

Abstract

A broad-band (2135-2165 cm(-1)) infrared spectrum of the CO-N2 van der Waals complex is obtained, using a tunable quantum cascade laser to probe a pulsed supersonic expansion from a slit jet source. Analysis of the spectrum results in the characterization of four new 'stacks' of rotational levels for CO-orthoN2 (all in the v(CO) = 1 upper state) and five new stacks for CO-paraN2 (three in the upper state and two in the vCO = 0 lower state). This considerably expands our knowledge of a rather fundamental weakly bound complex and should lead to improved determinations of the intermolecular forces governing interactions between the carbon monoxide and nitrogen molecules.

Ab initio study of the CO–N2 complex: a new highly accurate intermolecular potential energy surface and rovibrational spectrum

“…In a recent paper [10], an analysis of a new broad-band (2135-2165 cm −1 ) spectrum of CO-N 2 obtained using a tunable continuous-wave quantum-cascade laser and a pulsed supersonic slit-jet source was presented. Almost 100 new rovibrational levels were assigned to nine new stacks, of which four are in the excited state of CO-orthoN 2 , three in the excited state of CO-paraN 2 , and two in the ground state (ν CO = 0) of CO-paraN 2 .…”

Infrared spectrum and intermolecular potential energy surface of the CO–O2 dimer

“…2 and 3 of Ref. 34. The intensity in our spectrum derives from the CO vibrational transition moment, so in the free-rotor limit the selection rule is j(CO) = 1.…”

“…Spectra were recorded at the University of Calgary as described previously, [34][35][36][37] using a pulsed supersonic slit jet apparatus and a Daylight Solutions quantum cascade laser. The expansion mixture contained about 0.1 to 0.3% carbon monoxide plus 0.3 to 0.9% oxygen in helium carrier gas, and the jet backing pressure was 9 atmospheres.…”

“…This is the same expression as used previously for CO-N 2 , facilitating comparison of the two species. 26,[28][29][30][31][32][33][34] Results of the fits are given in Tables 3 and 4; we omit giving any uncertainties here because in many cases the number of levels fitted is not much larger than the number of parameters (and the Hamiltonian may not be fully appropriate). The rotational constant of the lowest K = 0 stack, 0.0772 cm -1 , may be compared to values of 0.0743 and 0.0708 cm -1 for CO-orthoN 2 and CO-paraN 2 , respectively.…”

“…Apart from spin effects, the spectrum and energy levels of CO-O 2 might be similar to those of CO-N 2 , which has been studied in detail. [26][27][28][29][30][31][32][33][34] The approach used to analyze CO-N 2 spectra has been simply to fit different stack origins, rotational and centrifugal distortion constants ( 0 , B, D, etc.) for each K-stack, and we adopt the same approach here for CO-O 2 .…”