MAGNETIC-FIELD EFFECT OF THE FLUORESCENCE OF GASEOUS NO2 EXCITED TO THE B-2(2) AND B-2(1) STATES

The effects of an external magnetic field (H) on the integrated intens ity and decay of the discrete (I-d(H)) and total (I-t(H)) fluorescence of NO2 vapor were examined under NO2 excitation in the A and B states by pulsed laser-light with different excitation wavelengths and pulse duration (tau(exc) approximate to 10 ns and 100 ps). The fluorescence intensity and decay of NO2 vapor have been measured as functions of e xternal magnetic field strength with excitation in the different spect ral regions belonging to the A <-- X and B <-- X transitions. The inte grated fluorescence intensity reduced by an external magnetic field. T he relation f(H)(= I-d(H)/I-d(0)) < r(H)(= I-t(H)/I-t(0)) is always sa tisfied. Field and pressure dependencies of r(H) are in a good agreeme nt with data obtained by Batler and Levy. Field and pressure dependenc ies of f(H) were carefully studied in the present work. Under microsec ond time resolution, the decay can be approximated by an exponential f unction in the absence and presence of a magnetic field for both the d iscrete and total fluorescence with respect to the data obtained by Fa tten et al. In this case, the lifetime of the NO2 fluorescence is not sensitive to the magnetic field within the variability of the excitati on wavelength, while the amplitude of the decay decreases in the prese nce of a magnetic field. Under subnanosecond time resolution, the deca y can be presented by a biexponential function in the presence of a ma gnetic field. The lifetime of the fast component is decreased by the m agnetic field. It was directly shown that the fast component induced b y the field defines the magnetic quenching of the NO2 fluorescence. Th ese results were explained by the direct mechanism (DM).