HIGH RESOLUTION RAMAN SPECTROSCOPY OF GASES: VIII. ROTATIONAL SPECTRA OF ACETYLENE, DIACETYLENE, DIACETYLENE-d2, AND DIMETHYLACETYLENE

The pure rotational Raman spectra of acetylene (C2H2), diacetylene (C4H2 and C4D2), and dimethylacetylene (C4H6) have been photographed with a 21-ft. grating spectrograph. The rotational constants were found to be B0(C2H2) = 1.1769 cm−1, B0(C4H2) = 0.14689 cm−1, B0(C4D2) = 0.12767 cm−1, and B0(C4H6) = 0.1122 cm−1. An analysis shows that r0(C—H) in diacetylene is shorter than in acetylene and cyanoacetylene; in dimethylacetylene at least one of the carbon–carbon bonds is longer than in the closely related molecule methylacetylene.