Infrared bands of CS2 dimer and trimer at 4.5 μm

Abstract

We report observation of new infrared bands of (CS2)2 and (CS2)3 in the region of the CS2 ν1+ ν3 combination band (at 4.5 m) using a quantum cascade laser. The complexes are formed in a pulsed supersonic slit-jet expansion of a gas mixture of carbon disulfide in helium. We have previously shown that the most stable isomer of (CS2)2 is a cross-shaped structure with D2d symmetry and that for (CS2)3 is a barrel-shaped structure with D3 symmetry. The dimer has one doubly degenerate infrared-active band in the ν1+ ν3 region of the CS2 monomer. This band is observed to have a rather small vibrational shift of -0.846 cm -1 . We expect one parallel and one perpendicular infrared-active band for the trimer but observe two parallel and one perpendicular bands. Much larger vibrational shifts of -8.953 cm -1 for the perpendicular band and -8.845 cm -1 and +16.681 cm -1 for the parallel bands are observed. Vibrational shifts and possible vibrational assignments, in the case of the parallel bands of the trimer, are discussed using group theoretical arguments.

Spectra of CO2‐Kr in the 4.3 μm region: Intermolecular Bend and Symmetry Breaking of the Intramolecular CO2 Bend

“…The vibrational and rotational parameters for CO 2 ‐ 84 Kr listed in Table 3 agree well with those from [1,2] but should be considered more reliable as both microwave data and a larger set of infrared data were included in the simulation. The higher order correction terms, B adj and C adj , were slightly larger than those reported for CO 2 ‐Xe [5] due to the larger mass difference between Kr isotopes. The isotopic band origin shift, Offset, was minimal with a shift of 0.0002 cm −1 between CO 2 ‐ 80 Kr and CO 2 ‐ 86 Kr and shifted downward with an increase in Kr atomic mass.…”

“…The ξ b parameters from Table 3 correspond to values of about 1.01 for ζ b , which is very similar to CO 2 ‐Ar [8] and slightly larger than CO 2 ‐Xe [5] . The splitting between i‐p and o‐p modes is determined to be 1.4184 cm −1 for CO 2 ‐Kr in the (01 1 0) state and 1.4283 cm −1 in the (01 1 1) state, with o‐p above i‐p.…”

“…For an isolated CO 2 molecule the bend is doubly degenerate, but in the dimers it splits into in‐plane (i‐p) and out‐of‐plane (o‐p) components. We have previously reported spectra in the region of the CO 2 ( v 1 , v 2 l 2 , v 3 )=(01 1 1)←(01 1 0) hot band near 2337 cm −1 for CO 2 ‐Ar, [8] −Ne, [9] −Xe, [5] −N 2 [10] and −CO [11] . Transitions from this excited state (01 1 0) to the combination state (01 1 1) exhibit b‐type selection rules, like the ν 3 fundamental.…”

“…The reason for this is the larger dependence of the intermolecular bend frequency on the Kr mass. The approach used to model the isotopic dependence of the spectrum is similar to that used previously for CO 2 ‐Xe [5] and the reader is referred to this work and the supplementary materials for more details.…”

The Ethylene–Carbon Dioxide Complex and the Double Rotor Model

“…It turns out that these differences can be remarkably well explained using the same hindered rotor model as long as we remember that only odd values are allowed for the CO2 rotational quantum number in the upper state of our transition (CO2 3), as compared to only even values in both the upper and lower states of their spectrum. Some other reported spectra of weakly-bound complexes containing ethylene include ethylene dimer and trimer, [2][3][4] ethylene-rare gas, [5][6][7] ethylene-nitrous oxide, 8 and ethylene-hydrogen halide. 9,10 2.…”