SYMMETRY BREAKING OF THE BENDING MODE OF CO2 IN THE PRESENCE OF Ar

Abstract

The weak infrared spectrum of CO 2-Ar corresponding to the (v 1 , v l2 2 , v 3) = (01 1 1) ← (01 1 0) hot band of CO 2 is detected in the region of the carbon dioxide ν 3 fundamental vibration (∼2340 cm −1), using a tunable OPO to probe a pulsed supersonic slit jet expansion. While this method was previously thought to cool clusters to the lowest rotational states of the ground vibrational state, here we show that under suitable jet expansion conditions, sufficient population remains in the first excited bending mode of CO 2 (1-2%) to enable observation of vibrationally hot CO 2-Ar, and thus to investigate the symmetry breaking of the intramolecular bending mode of CO 2 in the presence of Ar. The bending mode of CO 2 monomer splits into an in-plane and an out-of-plane mode, strongly linked by a Coriolis interaction. Analysis of the spectrum yields a direct measurement of the in-plane / out-of-plane splitting measured to be 0.8770 cm −1. This aspect of intramolecular interactions has received little previous experimental and theoretical consideration. Therefore, we provide an additional avenue by which to study the intramolecular dynamics of this simplest dimer in its bending modes. Similar results are obtained for CO 2-Ne.

Infrared spectra of (CO2)2 – Rg trimers, Rg = Ne, Ar, Kr, and Xe

“…High resolution infrared [3][4][5][6][7][8][9][10][11][12][13][14][15] and microwave 11,[16][17][18][19][20] spectroscopy of CO2-Rg dimers has revealed basic characteristics which are relevant for the trimers studied here. These include the intermolecular separations (C-Rg bond lengths) which are approximately (3.29, 3.50, 3.62, 3.81 Å) for the series (Ne, Ar, Kr, Xe), as well as the vibrational frequency shifts (relative to the free CO2 molecule) for the CO2 3 band which are (+0.130, -0.470, -0.884, -1.471 cm -1 ).…”

Observing the Completion of the First Solvation Shell of Carbon Dioxide in Argon from Rotationally Resolved Spectra

“…8 A T-shaped structure was established, with the Ar atom located to the 'side' of the CO2 molecule, adjacent to the C atom at an intermolecular separation of about 3.5 Å. Since then, there have been many further microwave 9,10 and infrared [11][12][13][14][15][16][17] studies. The trimer CO2-Ar2 has also been detected in the microwave 18 and infrared 2 regions.…”

“…Our spectra were recorded as described previously, 17,34 using a pulsed supersonic slit jet expansion probed by a rapid-scan optical parametric oscillator source. The slit width was set at 12.5 m, narrower than we have previously used in order to encourage the formation of larger clusters.…”