1. ROTATION-VIBRATIONAL ANALYSIS OF THE BANDS OF FORMALDEHYDE FALLING IN THE 3900 TO 5300 CM -1 REGION W.J. LAFFERTY Optical Technology Division NIST Gaithersburg, MD 20899 J.-M. FLAUD LISA CNRS/ Univ. Paris 12 et 7 61 Av. du General de Gaulle 94910 Creteil FRANCE R.L. SAMS AND S.W. SHARPE Pacific Northwest Laboratory P.O. Box 999 Richland, WA 99352

2. Background * Formaldehyde lines have been observed in urban atmospheres as well as over forest fires. *In this work, we discuss the spectrum of CH 2 O in the region 3900 to 5100 cm -1. * This overtone region contains a myriad of interacting bands linked by anharmonic and Coriolis resonances. *The region has been previously studied by T. Tipton et al. We have expanded their study greatly. * At this point 8 bands have been assigned and fit giving a standard deviation of 0.004 cm -1.

3. Molecular details C 2v symmetry Spin statistics: K a even 1; K a odd 3 Lowest vibration at ~ 1200 cm -1 A=9.41 cm -1 ; (B+C)/2 = 1.215 cm -1 Large centrifugal distortion effects About 30 vibrational levels in the region Every observed band perturbed and a challenge to assign

4. EXPERIMENTAL DETAILS Bruker IFS 120 HR Fourier transform spectrometer. Resolution 0.0030 cm-1 16 meter optical path. Pressures ranging from 0.1 Torr to 0.6 Torr. Calibration with CO 2 lines in spectrum.