Investigation of the electronic vibrational structure of furan by REMPI

Resonance-enhanced multiphoton ionization (REMPI) has been applied to detect the hot bands as well as the cold bands of the 1a2 →→ 3dxy(1A1) Rydberg transition of furan (jet-cooled, mass-analyzed). Based on the unambiguous assignment of the hot bands, a complete vibronic analysis is given for the cold bands of this transition (up to 4600 cm−1 above the origin). This analysis can be used for the interpretation of the vibrational structure in the X˜ 2A2 photoelectron band. The energy ordering of the five 3d Rydberg states is 1A2 ≈ 2A2 < A1 < B1 < B2. It is also shown that neutral CH is produced in the UV laser multiphoton photodecomposition of furan.