Rydberg spectra of trans -1,2-dibromoethylene

( 2 + 1 ) resonance-enhanced multiphoton ionization spectra of jet-cooled trans -1,2-dibromoethylene are reported for the first time. The two-photon spectral region between 149.7 and 141.2 nm was examined. A 4 p z ← π Rydberg transition between 66800 and 68 000 cm − 1 with A g excited state symmetry was analyzed, as well as two 4 f ← π Rydberg transitions with B g excited state symmetry and one 4 f ← π Rydberg transition with A g excited state symmetry between 68000 and 70 800 cm − 1 . All Rydberg transitions observed in this work belong to series that converge to the first ionization potential of the molecule. The short vibrational progressions observed involve two totally symmetric in-plane normal modes: C  C - H bending ( ν 3 ) and C  C - Br bending ( ν 5 ) with average excited state frequencies of 829 and 226 cm − 1 , respectively.