Vibronically excited 2-methylallyl radical [CH2C(CH3)CH2] at 4.6-5.6 eV has been studied by 1 + 1 and 2 + 2 resonance-enhanced multiphoton ionization (REMPI) spectroscopy. The 2-methylallyl radicals were produced by the flash pyrolysis of 3-bromo-2-methylpropene in a supersonic-jet expansion. The 2 + 2 REMPI spectrum of 2-methylallyl radical at 38 000-40 700 cm(-1) is identified as (B) over tilde (1 (2)A(1)) <-- <(X)over tilde> (1 (2)A(2)) transition, i.e., the excitation of a nonbonding electron to the 3s Rydberg state (3s <-- n). Seven lowest-lying electronic states with excitation energy below 6 eV have been calculated in an MRCI level. Two new electronic bands have been observed at 38 500-41 000 cm(-1) by 1 + 1 REMPI spectroscopy and assigned to <(C)over tilde>(1 B-2(2)) <-- <(X)over tilde>(1 (2)A(2)) and (E) over tilde (2 (2)A(2)) <-- <(X)over tilde> (1 (2)A(2)). Much broader 1 + 1 REMPI signals at 41 000-43 5 00 cm(-1) with HWHM of similar to80 cm(-1) for each vibronic band could be due to (D) over tilde (2 B-2(2)) <-- (1 (2)A(2)) and/or <(F)over tilde>(3 B-2(2)) <-- <(X)over tilde>(1 (2)A(2)) via an intensity borrowing from (C) over tilde (1 B-2(2)) <-- <(X)over tilde>(1 (2)A(2)). Taking the computed geometries and vibrations of the ground- and excited electronic states, Franck-Condon factors (FCFs) have been calculated. Combining the FCFs with calculated excitation energies and oscillator strengths of the six electronic states at 4-6 eV, predicted spectral patterns have been used to assist spectroscopic analysis for the observed vibronic spectra of 2-methylallyl radical. (C) 2003 American Institute of Physics.