Rotation-Vibration Constants of Acetylene

Abstract

The study of the absorption spectrum previously reported has been extended to include the 1900- to 2200- and the 4400- to 6750-cm-1 regions. Rotational analysis provides 20 states from which the following constants are determined: α1=6.82, α2=6.30, α3=5.60, α4=-1.30, α5=-2.20×10-3 cm-1 and Be=1.18240 cm-1. This value was used with Be values for C2HD and C2D2 to determine the bond length of re(C-H)=1.0603 and re(C≡C)=1.2034 Å.A total of 46 states was available, from this and other work, to determine a set of vibrational constants. About one-half of the 23 constants have been determined with acceptable precision. The remaining constants are still in doubt due, primarily, to resonances.