Knowledge Bank

The chemiluminescent reactions of boron with $O2$ and $N2O$ have been studied over a pressure range from $10-5$ to 10 torr. At the lowest pressure boron atoms intersect a tenuous atomsphere of oxidant gas ($10-5$ to $10-3$ torr) forming ground and excited state boron oxide products; at higher pressures boron atoms are entrained under controlled conditions is argon (0.5 to 10 torr) and the resultant mixture oxidized. These boron oxidations are characterized by the following unusual features: (1) One observes rapid V-E intramolecular energy transfer at pressures as low as $10-5$ torr corresponding to the process $BO(X2\Sigma +,v\prime \prime =17)\to BO(A2\pi ,v\prime =4)$; this energy transfer is highly temperature and pressure dependent. The intromolecular energy transfer rate must considerably exceed the hard sphere gas kinetic collision rate. (2) At higher pressures (argon buffer gas) these non-equilibrium product distributions persist reflecting a strong coupling butween the $A2\pi$ and $X2\Sigma +$ states. (3) Computer simulations of the observed spectra reflect the strong A-X coupling indicating the possibility of differing radiative lifetimes for the $^{2}\pi _{1/2} $ and $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\pi 3/2$ components of the $A2\pi$ state; the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\pi 3/2-X2\Sigma +$ transition appears to have the shorter lifetime.