Experimental and Theoretical Study of the Broadening and Shifting of N2H+ Rotational Lines by Helium |
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Authors: | Dr. Giovanni Buffa Dr. Ottavio Tarrini Prof. Luca Dore Prof. Markus Meuwly |
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Affiliation: | 1. IPCF‐CNR, Largo Pontecorvo 3, I‐56127 Pisa (Italy);2. Dipartimento di Chimica ”G. Ciamician”, Universit‘a di Bologna, Via Selmi 2, I‐40126 Bologna (Italy);3. Department of Chemistry, Klingelbergstr. 80, 4056 Basel (Switzerland), Fax: (+41)?61?267?38?21;4. Department of Chemistry, Brown University, Providence RI 02912 (USA) |
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Abstract: | Pressure broadening and pressure shift of N2H+ rotational lines perturbed by collisions with He are studied for the first time using experiment and theory. Results are reported from measurements at 88 K for the rotational transitions ${j = 3 leftarrow 2}$ , ${4 leftarrow 3}$ , ${5 leftarrow 4}$ and ${6 leftarrow 5}$ with frequencies ranging from 0.28 to 0.56 THz. The agreement between experiment and theoretical data derived from close coupling calculations confirms the reliability of a theoretical framework used for state‐to‐state transition rates of interest in the interpretation of spectroscopic data from interstellar molecular clouds. The influence of hyperfine effects on shifts and widths of the rotational lines is discussed in detail. Although in principle possible, experiment and theoretical considerations lead to the conclusion that hyperfine effects only play a minor role. |
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Keywords: | ab initio calculations cluster compounds helium hyperfine effects rotational spectroscopy |
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