Ground state relaxation measurements by laser-induced depopulation

Abstract

We have directly measured the repopulation rate for an individual rotational level in the electronic ground state of a homonuclear molecule. A pulsed dye laser was used to depopulate (v^″, J^″) level of Na₂ by pumping a transition of the form (v′, J′) ← (v^″, J^″) in the B¹Π_u‐X¹Σ⁺_g blue–green band system. The (v^″, J^″) state was repopulated by collisions with other sodium species and with an argon buffer gas. The transmission of a second, delayed, pulsed dye laser was monitored, serving as a probe of the (v^″, J^″) state’s population at various delay times. The argon pressure was varied and the procedure repeated. The Na₂–argon collision cross section may also be determined by this method.