Collisional energy transfer from excited nitrogen dioxid

The radiative lifetimes of gaseous nitrogen dioxide excited by pulsed, tunable dye laser radiation are determined for excitation wavelengths ranging from 400 to 750 nm. When the data are expressed in the form of zero-pressure radiative rate constants (k$sb0$ / s$sp{-1}$), they fit a linear equation with respect to excitation energy (X$sb{rm L}$ / cm$sp{-1}$): k$sb0$ = (0.504 $pm$ 0.168) (X$sb{rm L} -$ X$sb0$) + (7.96 $pm$ 1.82) $times$ 10$sp3$, given an origin energy $Xsb0$ of 9,710 cm$sp{-1}$. This fit predicts a radiative lifetime of 64 $mu$s for 400 nm excitation and 102 $mu$s at 750 nm. The effects of pressure, observation delay time, and wavelength range of the fluorescence detection apparatus are determined for both radiative lifetime and quenching constant.;Dispersed fluorescence spectra from excited nitrogen dioxide are analyzed into three-parameter functions that approximate the corresponding excited state population distributions. Energy transfer from nitrogen dioxide excited at 532 nm and colliding with thirteen buffer gases is studied by this population deconvolution method. The energy removal rate constant for nitrogen dioxide as a buffer gas is (6.92 $pm$ 0.66) $times$ 10$sp{-8}$ cm$sp{-1}$ cm$sp3$ molecule$sp{-1}$ s$sp{-1}$, which corresponds to (629 $pm$ 60) cm$sp{-1}$ removed per hard-sphere collision based on a collision rate constant of 1.10 $times$ 10$sp{-10}$ cm$sp3$ s$sp{-1}$. Neon quenches nitrogen dioxide least efficiently among the buffer gases studied; its energy transfer rate constant of (2.16 $pm$ 0.18) $times$ 10$sp{-8}$ cm$sp{-1}$ cm$sp3$ molecule$sp{-1}$ s$sp{-1}$ gives only (206 $pm$ 17) cm$sp{-1}$ removed per hard-sphere collision for a collision rate constant of 1.05 $times$ 10$sp{-10}$ cm$sp3$ s$sp{-1}$. The most efficient quencher is sulfur dioxide with an energy transfer rate constant of (15.42 $pm$ 1.43) $times$ 10$sp{-8}$ cm$sp{-1}$ cm$sp3$ molecule$sp{-1}$ s$sp{-1}$, or (1390 $pm$ 130) cm$sp{-1}$ removed per hard-sphere collision when the collision rate constant is taken as 1.11 $times$ 10$sp{-10}$ cm$sp3$ s$sp{-1}$. The energy removal rate constants increase in the order Ne $<$ Ar $<$ Kr $<$ Xe $<$ He $<$ CO $<$ N$sb2$ $<$ O$sb2$ $<$ NO $<$ NO$sb2$ $<$ CO$sb2$ $<$ SF$sb6$ $<$ SO$sb2$. The energy transfer rate constant is strongly correlated with the number of degrees of freedom of the buffer molecule and with low vibrational frequencies of the buffer molecule.;Population deconvolution from excited nitrogen dioxide fluorescence spectra is again employed to find energy removal rate constants for the NO$sb2 sp*$-NO$sb2$ collisions, excited by dye laser at 475.34, 435.04, and 400.00 nm. The energy transfer rate constant increases with decreasing excitation wavelength to (32.6 $pm$ 2.2) $times$ 10$sp{-8}$ cm$sp{-1}$ cm$sp3$ molecule$sp{-1}$ s$sp{-1}$ at 400.00 nm, or (2960 $pm$ 200) cm$sp{-1}$ per hard-sphere collision. The energy removal rate constant between 400 and 532 nm excitation increases as the (3.6 $pm$ 0.4) power of the excitation photon energy.