Optical-optical double-color and double-resonance multiphoton ionization spectrum of NO2

The optical-optical double resonance multiphoton ionization (OODR-MPI) technique has been applied to the study of the Rydberg states of nitrogen dioxide. The results show that NO2 molecule is ionized though a 1 + 3 + 1 double resonance hv, multiphoton ionization process in 605-675 nm probe wavelength region. The ionization pathway is: NO2 (X(2)A(1))->(NO2)-N-h nu 1 (A(2)B(2))->(NO2)-N-3h nu 2(3p sigma(u))->(NO22)-N-h nu 1 + e. The OODR-MPI spectrum corresponds to the excitation of NO2 3p sigma(u) Rydberg state by a three photon process. The value (omega(1) = (1422.5 +/- 23.5) cm(-1) and omega(2) = (590.5 +/- 4.9) cm(-1) of symmetric stretching and bending vibration frequencies of this Rydberg state are presented. The position of the band origin and the quantum defect of Spa Rydberg state are obtained to be (58331 +/- 71) cm(-1) and 0.69, respectively.