Quenching and excitation-transfer processes involving the $3{}_{}{}^2{}_{}{}^{}P$ and $3{}_{}{}^2{}_{}{}^{}D$ states of the Li atom are studied in a temperature-controlled heat-pipe oven with the use of two-step laser excitation of the $4{}_{}{}^2{}_{}{}^{}S$ state followed by radiative cascade towards the $3{}_{}{}^2{}_{}{}^{}P$ state. Numerical identification of the collision-induced $3{}_{}{}^2{}_{}{}^{}D\to 2{}_{}{}^2{}_{}{}^{}P$ fluorescence with a three-level model allows the determination of radiative coefficients and collisional rate coefficients. $4{}_{}{}^2{}_{}{}^{}S$, $3{}_{}{}^2{}_{}{}^{}D$, and $3{}_{}{}^2{}_{}{}^{}P$ radiative lifetimes are found to be in agreement with accepted values. Quenching and excitation transfer strongly depend on the colliding atoms. Rate coefficients for the $3{}_{}{}^2{}_{}{}^{}D\to 3{}_{}{}^2{}_{}{}^{}P$ excitation processes induced by Li, He, and Ne ground-state atoms are measured in the ratio 1.05: 0.23: 0.02 expressed in ${10}^{-9\mathrm{}}$ ${\sec }^{-1\mathrm{}}$ ${\mathrm{cm}}^3$.

• Received 3 March 1982

DOI:https://doi.org/10.1103/PhysRevA.26.1431