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 Title: JET-COOLED INFRARED LASER SPECTROSCOPY IN THE UMBRELLA ν2 VIBRATION REGION OF NH3: IMPROVING THE POTENTIAL ENERGY SURFACE MODEL OF THE NH3−Ar VAN DER WAALS COMPLEX Author(s): Asselin, Pierre Contributor(s): van der Avoird, Ad; Loreau, Jérome; Potapov, Alexey; Jabri, Atef Subject(s): Clusters/Complexes Abstract: Taking advantage of our sensitive laser spectrometer coupled to a pulsed slit jetfootnote{P. Asselin, Y. Berger, T. R. Huet, R. Motiyenko, L. Margulès, R. J. Hendricks, M. R. Tarbutt, S. Tokunaga, B. Darquié, PCCP 19, 4576 (2017),} we recorded near the nub{2} vibration a series of rovibrational transitions of the chem{NH_3-Ar} van der Waals (vdW) complex. These transitions involve in the ground vibrational state several internal rotor states corresponding to the orthochem{NH_3} and parachem{NH_3} spin modifications of the complex. They are labeled by $Sigma$$_{a}(j,k), Sigma$$_{s}$(j,k), $Pi$$_{a}(j,k) and Pi$$_{s}$(j,k) where $Sigma$(K=0) and $Pi$(K=1) indicate the projection K of the total rotational angular momentum J on the vdW axis, the superscripts s and a designate a symmetric or antisymmetric chem{NH_3} inversion wave function, and j, k quantum numbers indicate the correlation between the internal-rotor state of the complex and the j, k rotational state of the free chem{NH_3} monomer. Five bands have been identified, only one of which was partly observed beforefootnote{G. T. Fraser, A.S. Pine and W. A. Kreiner, J. Chem. Phys. 94, 7061 (1991).}. They include transitions starting from the $Sigma$$_{a}(j=0 or j=1) state without any internal angular momentum, consequently they can be assigned from the band contour of a linear-molecule-like K=0, DeltaJ=1 transition. The energies and splittings of the rovibrational levels of the nub{2}=1$$leftarrow$0 spectrum derived from the analysis of the $Pi$$_{s}, Sigma$$_{s}$(j=1)$leftarrow$ $Sigma$$_{a}(j=0), k=0 bands and mostly of the Sigma$$_{s}$, $Pi$$_{s} and Sigma$$_{a}$(j=1)$leftarrow$$Sigma$$_{a}$(j=1), k=1 bands bring relevant information about the nub{2} dependence of the chem{NH_3-Ar} interaction, the rovibrational dynamics of the chem{NH_3-Ar} complex and provide a sensitive test of a recently developed 4D potential energy surface that includes explicitly its dependence on the umbrella motionfootnote{J. Loreau, J. Liévin, Y. Scribano and A. van der Avoird, J. Chem. Phys. 141, 224303 (2014).}. Issue Date: 6/23/2017 Publisher: International Symposium on Molecular Spectroscopy Citation Info: APS Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/96865 DOI: 10.15278/isms.2017.FD07 Date Available in IDEALS: 2017-07-27
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