Femtosecond ground state dynamics of gas phase N 2O 4 and NO 2

Abstract

Non-resonant femtosecond time-resolved four-wave mixing (FWM) data on gas phase NO 2 and N 2O 4 are presented. The initial rotational dephasing is observed during the first picosecond after excitation. Fast vibrational dynamics (average value 133±1 fs beats) are observed for dinitrogen tetroxide and are assigned to the ν 3 N–N stretching mode in the ground state ( 1 A g ) . Rotational revivals on the picosecond time scale are recorded for both samples. No evidence of a long-lived excited state participation was found using photon echo (PE) or virtual echo (VE) pulse sequences with 800 nm laser pulses, however, NO 2 photoproducts were observed following N 2O 4 excitation.