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 Title: INTERMOLECULAR DYNAMICS OF BINARY NH3-RARE GAS COMPLEXES IN THE ν2 UMBRELLA MODE REGION OF NH3 : ROVIBRATIONAL JET-COOLED LASER SPECTROSCOPY AND AB INITIO CALCULATIONS Author(s): Asselin, Pierre Contributor(s): van der Avoird, Ad ; Loreau, Jerome ; Berger, Yann ; Belkhodja, Yacine Subject(s): Clusters/Complexes Abstract: The large number of spectroscopic and theoretical studies of \chem{NH_3}-Rg complexes reported for three decades clearly proves that they are good prototypes to investigate intermolecular dynamics of van der Waals interactions. The inversion coordinate for which the inversion-tunneling splitting in \chem{NH_3} is not quenched in the case of \chem{NH_3}-Rg represents a valuable probe of asymmetry in the intermolecular potential energy surface (IPES).\footnote{G. T. Fraser, D. D. Nelson Jr, A. Charo and W. Klemperer, J. Chem. Phys. 82, 2535 (1985).} A recent high resolution infrared laser jet- cooled study realized in the \nub{2} umbrella mode region of \chem{NH_3}-Ar enabled to detect five ortho and para bands and to provide accurate band centres and upper state rotational constants for the ortho ones.\footnote{P. Asselin, Y. Belkhodja, A. Jabri, A. Potapov, J. Loreau and A. van der Avoird, Mol . Phys. 116, 3642 (2018)} The puzzling para bands observed in the region of the lower and upper components of the inversion splitting doublets have been assigned by comparison with calculations of vibration-rotation-tunneling (VRT) levels based on a 4D PES that includes the umbrella inversion motion.\footnote{J. Loreau and A. van der Avoird, J. Chem. Phys. 143,184303 (2015)} The present study aims to investigate more in detail the intense ortho bands of the \chem{NH_3}-Rg family (Rg= Ne, Ar, Kr, Xe) taking advantage of recent improvements in the pulsed slit expansion to reduce line widths and to increase gain in absorption. These advances enabled to derive accurate excited rotational and quartic parameters and l-type doubling constant q for the four binary \chem{NH_3}-Rg complexes from rovibrational analyses of the ortho $\Pi$$_s(j=1,k=0) \leftarrow \Sigma$$_a$(j=1,k=0) transition. Using a pseudodiatomic model, structural parameters and force constants of the \chem{NH_3}-Rg family could be estimated from the experimental set of spectroscopic constants obtained and then compared with those calculated using ab initio VRT levels, transition frequencies and line strengths from 4D PES of \chem{NH_3}-Rg. The predictive character of the IPES is discussed on the grounds of band origins, rovibrational states and l-type doubling contribution. Issue Date: 23-Jun-20 Publisher: International Symposium on Molecular Spectroscopy Citation Info: APS Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/107315 Date Available in IDEALS: 2020-06-26
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