Millimeter Wave Spectrum of Formaldehyde

Abstract

A Stark modulation-type spectrograph has been constructed. Millimeter wave klystrons are used as the power source. The sensitivity of the spectrograph is about 2×10 -7 cm -1 at 70 Gc, when the spectral lines are displayed on a cathode-ray oscilloscope with a sweep rate of 1 cps. R -branch transitions 1 01 ←0 00 of the formaldehyde isotopic species H 2 C 13 O, H 2 CO 18 , HDCO, D 2 CO, D 2 C 13 O and D 2 CO 18 have been measured and their rotational constants have been determined. The observed inertia defects of D 2 CO, H 2 C 13 O and H 2 CO 18 are shown to be in good agreement with the predicted theoretical values. From the observed rotational constants the r z -structures of formaldehyde are determined to be