# Measurement of the first excited bending state of Ar-CO in the IR region

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 Title: Measurement of the first excited bending state of Ar-CO in the IR region Creators: Hilpert, G.; Havenith, M.; Petri, M.; Urban, W. Issue Date: 1993 Publisher: Ohio State University Abstract: By means of infrared diode laser spectroscopy we measured 17 lines of the transition from the first excited bending state $K=1$ to the $v_{CO}=1, K=0$ state of $Ar-CO$ in a molecular jet. 5 lines were attributed to the P branch and 12 to the R branch of that transition. Unfortunately, the Q branch was covered by a strong CO line. The band origin is at $2154.607 cm^{-1}$, which implies that the $K= 1$ first excited bending state of $Ar-CO$ is $14.2 cm^{-1}$ higher in energy than the $K=1$ ground state. This is in very good agreement with the theoretical calculations of Tennyson et al. [1]. We also introduce a new modulation technique for diode laser spectroscopy in a molecular jet. By means of an AC discharge we modulate the concentration of the van der Waals clusters in our jet. By demodulating the signal at the sum of the concentration modulation and the usual fm-modulation with lock in the signal to noise ratio can be improved significantly compared to the usual fm-modulation technique. Description: $^{1}$. I. Tennyson, S Millee and B.T. Sutcliffe J. Chem. Soc. Faraday Trans. II, 84, 1295 (1985). Author Institution: Institut f\""{u}r Angewandte Physik URI: http://hdl.handle.net/1811/18620 Other Identifiers: 1993-TD-11