Energy transfer in monochromatically excited nitric oxide: A2Σ+ and B2Π

Excitation of NO molecules into specific vibration‐rotation levels of the A²Σ⁺ and B²Π electronic states by absorption of atomic lines has been studied under various experimental conditions by observing the steady‐state fluorescence spectra of the ${\mathrm{(A\hspace{0.17em}}}^2{\Sigma }^{+}{\mathrm{-X\hspace{0.17em}}}^2\mathrm{\Pi )}$ and ${\mathrm{(B\hspace{0.17em}}}^2{\mathrm{\Pi -X\hspace{0.17em}}}^2\mathrm{\Pi )}$ bands. Excitation of the ${\mathrm{A\hspace{0.17em}}}^2{\Sigma }^{+}\text{, v′=0–3}$ and ${\mathrm{B\hspace{0.17em}}}^2\text{Π, v′=3, 4}$ levels was achieved. The fluorescence from $\mathrm{NO}{\mathrm{\hspace{0.17em}A\hspace{0.17em}}}^2{\Sigma }^{+}\text{, v′=0–3}$ was found to be quenched by NO X²Π with an effective cross section of 25 Ų. The fluorescence from $\mathrm{NO}{\mathrm{\hspace{0.17em}B\hspace{0.17em}}}^2\text{Π, v′=0, 3, 4}$ was found to be quenched by NO X²Π with effective cross sections of 16, 21, and 20 Ų, respectively. The anomalously efficient vibrational relaxation of $\mathrm{NO}{\mathrm{\hspace{0.17em}A\hspace{0.17em}}}^2{\Sigma }^{+}\text{, v′=1}$ by NO X²Π was found to be one aspect of an efficient electronic energy exchange process. The cross sections for exchange of electronic energy between ${}^{14}{\mathrm{N}}^{16}\mathrm{O}{\mathrm{\hspace{0.17em}A\hspace{0.17em}}}^2{\Sigma }^{+}\text{, v′=0}$ and 1 and ${}^{15}{\mathrm{N}}^{16}\hspace{0.17em}\mathrm{O}{\mathrm{X\hspace{0.17em}}}^2\text{Π, v″=0}$ were found to be $\text{12 ± 3, 7 ± 4}$ , and $\text{1.7 ± 0.3\hspace{0.17em}}{\mathrm{\AA }}^2$ for the ${}^{14}{\mathrm{N}}^{16}\mathrm{O}{\text{A, v′=1→}}^{15}{\mathrm{N}}^{16}\mathrm{O}{\text{, A, v′=1,}}^{14}{\mathrm{N}}^{16}\mathrm{O}{\text{A, v′=0→}}^{15}{\mathrm{N}}^{16}\mathrm{O}\text{A, v′=0}$ , and ${}^{14}{\mathrm{N}}^{16}\mathrm{O}{\text{A, v′=1→}}^{15}{\mathrm{N}}^{16}\mathrm{O}\text{A, v′=0}$ processes, respectively. A transition dipole‐transition dipole interaction is proposed for this transfer process. Rates of electronic energy transfer from NO A²Σ⁺ to NO B²Π, and vice versa, in collision with NO X²Π, were also measured.