Knowledge Bank

Phase-shift measurements over a wide range of modulation frequencies have been made, using the apparatus designed by $Lawrence,1$ to determine radiative lifetimes of emission spectra in the vacuum ultraviolet. Spectra were excited by an r.f.-modulated electron beam in NO and CO at very low pressures. The use of many different modulation frequencies is essential for the analysis of radiative cascading from higher excited states. The principal results are tabulated here: ""[FIGURE]"" $$\begin{array}{lll}\multicolumn{1}{c}{Transition}& \multicolumn{1}{c}{r_{v}(\times 10^{-9},sec)}& f_{el}(abs.)\NO\ D\ ^{2}\Sigma^{+} - X\ ^{2}\Pi\ (v^{\prime}=1)&\ \ 7.5& \leq 0.035\NO^{+}\ A\ ^{1}\Pi\ - X\ ^{1}\Sigma^{+}\ (v'=0,1)& 52 &\ \ 0.014\CO\ A\ ^{1}\Pi - X\ ^{1}\Sigma^{+}(v'=0)& 11.2 &\ \ 0.075\CO\ A\ ^{1}\Pi\ - X\ ^{1}\Sigma^{+}\ (v'=1,2)& 10.0&\ \ 0.088\CO\ B\ ^{1}\Sigma^{+}\ - X\ ^{1}\Sigma^{+}\ (v^{\prime}=0)&17&\ \ 0.012\end{array}$$ Relative intensities were measured to determine vibrational branching ratios and to derive Franck-Condon factors for excitation and for emission. The work was supported by NASA Grant NsG-414.