RESONANCE IONIZATION SPECTROSCOPY OF CYANOGEN

Strong (1+2) resonance-enhanced multiphoton ionization (REMPI) spectra have been recorded for cyanogen resonantly excited by single photon a bsorption on vibronically allowed transitions to the (A) over tilde (1 ) Sigma(u)(-) and (B) over tilde (1) Delta(u) electronic states at wav elengths from 205 to 220 nm. A previously unreported Fermi resonance b etween the nu(2) and 4 nu(5) vibrational modes of the (A) over tilde s tate is observed for the rotationally resolved spectra of transitions that involve excitations of the nu(2) mode. New measurements of vibrat ional and rotational spectroscopic constants are reported for the (A) over tilde and (B) over tilde electronic states. A detection limit of 120 ppb measured for (1+2) REMPI of cyanogen is an order of magnitude larger than typical (2+1) REMPI detection limits for other aliphatic c ompounds. (C) 1998 American Institute of Physics. [S0021-9606(98)01109 -X].