Ab initio potential energy surface and rovibrational spectra of He–CO2

Abstract

The potential energy surface for the He–CO2 van der Waals complex is calculated using the fourth-order Moller–Plesset (MP4) perturbation theory with a large basis set containing bond functions. The interaction energies are obtained by the supermolecular approach with the full counterpoise correction for the basis set superposition error. The MP4 interaction energies are then fitted to an exponential-spline-Morse–Morse-spline-van der Waals potential form. The ab initio potential energy surface contains two local minima corresponding to the T-shaped and linear structures. The T-shaped minimum is the global minimum with the well depth of 44.41 cm−1 at R(He–C)=3.10 Å. The linear minimum has a well depth of 27.69 cm−1 at R(He–C)=4.26 Å. A potential barrier that separates the two minima is located at R(He–C)=4.10 Å and θ=39° with a height of 19.81 cm−1. The rovibrational energy levels of He–CO2 with CO2 at its ground state and υ3 excited state are calculated using the vibrational self-consistent field configuration-interaction approach. Our calculated results show that the potential supports five vibrational bound states. The zero-point energy is 28.60 cm−1. The first excited bend frequency is 8.67 cm−1, which is very close to the experimental estimated value of about 9±2 cm−1. The calculated transition frequencies and spectroscopic constants are in good agreement with the experimental values.

High resolution infrared spectra of a carbon dioxide molecule solvated with helium atoms

“…The energy of the lowest bound state relative to dissociation was calculated to be around Ϫ16 to Ϫ18 cm Ϫ1 . 15,17 The large differences between D 0 and D e ͑Ϸ17 versus 48 cm Ϫ1 ͒, and between R 0 and R e ͑3.6 versus 3.1 Å͒, are reminders of the floppy nature of the He-CO 2 complex.…”

Experimental He-pressure broadening for the R(10) and P(2) lines in the ν3 band of 13CO2, and experimental pressure shifts for R(10) measured at several temperatures between 300K and 100K

“…The complexes of CO 2 with rare gas atoms represent a very interesting intermediate case between the semi-rigid and nearly free internal rotor limits. Several empirical [2] and ab initio [3][4][5] intermolecular potential energy surfaces (PESs) have been published for the He-CO 2 system. Some of these PESs present salient differences for the attractive part of the intermolecular potential.…”

“…The intermolecular interaction between carbon dioxide (CO 2 ) and helium (He) has been extensively studied from a theoretical point of view [1][2][3] due to the role of this rather simple system as a fundamental reference system for empirical and ab initio determination of intermolecular forces. The complexes of CO 2 with rare gas atoms represent a very interesting intermediate case between the semi-rigid and nearly free internal rotor limits.…”

A new ab initio potential energy surface and infrared spectra for the Ne–CS2 complex

“…At the same time, some theoretical researches have performed the construction of the ab initio potential energy surface (IPES) and the calculation of the rovibrational energy levels. In the previous theoretical calculations [9][10][11][12][13][14][15][16][17], ab initio PES were obtained by assuming the CO 2 monomer as a rigid rotor, which is not sufficient for describing infrared spectra as the transition in the intramolecular vibrational mode is usually involved [25,26]. One effective way is to take into account the influence of intramolecular vibrational mode on the potential energy surface and dynamical calculations [27,28].…”

“…Such studies taking into account of discrete spectra can greatly enhance our understanding on the intermolecular potentials and dynamics of these weakly bound molecules. Carbon dioxide complexes have been completely investigated experimentally [1][2][3][4][5][6][7][8] and theoretically [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], since CO 2 is one of the most significant absorbers of infrared radiation in the earth's atmosphere and interstellar chemistry. As an analog of CO 2 , carbon disulfide is also intriguing because sulfur itself is a key element at the ground level of our atmosphere [24].…”