# STARK SPECTROSCOPY WITH THE CO LASER: THE DIPOLE MOMENT OF $H_{2}CO$ IN THE $\nu_{3}$ AND $\nu _{5}$ EXCITED VIBRATIONAL STATES

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 Title: STARK SPECTROSCOPY WITH THE CO LASER: THE DIPOLE MOMENT OF $H_{2}CO$ IN THE $\nu_{3}$ AND $\nu _{5}$ EXCITED VIBRATIONAL STATES Creators: Allegrini, M.; Johns, J. W. C.; McKellar, A. R. W. Issue Date: 1977 Publisher: Ohio State University Abstract: We have recently studied the $\nu_{3}$ fundamental and $\nu_{5} \leftarrow \nu_{6}$ combination bands of $H_{2}CO$ using the technique of intracavity laser Stark spectroscopy, $\nu_{3} (1500.17 cm.^{-1})$ is the $CH_{2}$ scissoring motion, $\nu_{6} (1249.09$ $cm^{-1})$ the $CH_{2}$ rocking vibration, and $\nu_{5} (2843.32 cm^{-1})$ the antisymmetric CH stretch. Previously, values of the dipole moment have been measured for the ground, $\nu_{4}$, and $\nu_{6}$ states of $H_{2}CO$ by molecular beam electric $resonance^{1}$ and for $\nu_{2}$ by our laser Stark studies. The present work brings to 5 (out of 6) the number of vibrational modes for which the dipole moment is known. Extensive results are also available for $D_{2}CO$ and $HDCO$; thus formaldehyde is probably the best characterised polyatomic molecule for the vibrational dependence of the dipole moment, and It would appear to present an interesting challenge for ab initio calculation. Description: $^{1}$ B. Fabricant, D. Krieger, and J. S. Muenter, J. Chem. Phys. (to be published). Author Institution: Herzberg Institute of Astrophysics, National Research Council of Canada URI: http://hdl.handle.net/1811/9988 Other Identifiers: 1977-FB-9