VIBRONIC ANALYSIS OF 4-FLUOROINDOLE, 5-FLUOROINDOLE, AND 6-FLUOROINDOLE

The excitation spectra of 4-, 5-, and 6-fluoroindole have been obtaine d with jet-cooled one-color resonant two-photon ionization (1C R2PI) t ime-of-flight mass spectrometry (TOFMS). The 1C R2PI spectra have been vibronically analyzed in the spectral region of 0(0)(0) to 0(0)(0) 842 cm(-1) in 4-fluoroindole and 0(0)(0) to 0(0)(0) + similar to 1100 cm(-1) in 5- and 6-fluoroindole. All transitions observed in the 4-, 5 -, and 6-fluoroindole excitation spectra are assigned as (1)L(b) <-- ( 1)A' transitions. Assignments of both ground- and excited-state vibrat ional modes were based upon those previously assigned for indole.(4,9) As with indole, the ground-state vibrational frequencies were also ca lculated using ab initio methods as well as being obtained from infrar ed and Raman studies.