FOURIER-TRANSFORM FAR INFRARED-SPECTROSCOPY OF A C4 BENDING MODE

A study of the Fourier transform far infrared spectrum of the C4 radical produced by trapping the products of the vacuum ultraviolet photolysis of 1,3-butadiene and acetylene in Ar at 10 K has resulted in the identification for the first time of a bending vibration at 172.4 cm-1. The assignment is confirmed by C-13 isotopic data; is consistent with the earlier identification of the antisymmetric C = C stretching mode at 1543.4 cm-1; and is in agreement with the predictions of ab initio calculations for linear C4.