EDP Sciences
Free access
Volume 425, Number 2, October II 2004
Page(s) 767 - 772
Section Atomic, molecular and nuclear data
DOI http://dx.doi.org/10.1051/0004-6361:20040532

A&A 425, 767-772 (2004)
DOI: 10.1051/0004-6361:20040532

Millimeter-wave spectroscopy of HC $\mathsf{_5}$N in vibrationally excited states below 500 cm $\mathsf{^{-1}}$

K. M. T. Yamada1, C. Degli Esposti2, P. Botschwina3, P. Förster1, L. Bizzocchi2, S. Thorwirth1 and G. Winnewisser1

1  I. Physikalisches Institut, Universität zu Köln, Zülpicherstraße 77, 50937 Cologne, Germany
2  Dipartimento di Chimica "G. Ciamician", Università di Bologna, Via F. Selmi 2, 40126 Bologna, Italy
    e-mail: claudio.degliesposti@unibo.it;bizzo@ciam.unibo.it
3  Institut Für Physikalische Chemie, Universität Göttingen, Tammannstraße 6, 37077 Göttingen, Germany

(Received 26 March 2004 / Accepted 3 June 2004)

The rotational spectrum of the semistable HC 5N molecule has been investigated in the millimeter-wave region for eight excited bending states which lie below 500 cm -1, namely $v_{11} =1,\,2,\,3$, and 4, v10=1, v9=1, ( v10 = 1, v11 = 1), and ( v10 = 1, v11 = 2). Transitions up to $J = 101 \leftarrow 100$ were measured, reaching a frequency as high as 270 GHz. The set of spectroscopic constants determined in the present work makes it possible to predict with much improved accuracy the transition frequencies of millimeter-wave lines produced by vibrationally excited HC 5N in hot core molecular sources and circumstellar shells. In addition, results of extensive CCSD(T) calculations are presented, which yield accurate term values for low-lying bending vibrational states.

Key words: molecular data -- methods: laboratory -- techniques: spectroscopic -- radio lines: ISM

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