Knowledge Bank

Stimulated Emission Pumping (SEP) is a variant of Optical-Optical Double Resonance, utilizing two pulsed dye lasers. The first laser, the PUMP, is tuned to populate a single rotation-vibration level of the $A~1Au$ state of $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C2H2$. The second laser, the DUMP, stimulates emission downward from the prepared level into a vibrationally excited level of the electronic ground state, $X~1\Sigma g+$. The SEP signal is seen as a decrease in $A\to X$ side fluorescence when the DUMP laser is on resonance. Because the A-state of acetylene is trans-bent in its equilibrium configuration, Franck-Condon factors permit us to DUMP into vibrational levels with primarily trans-bending character. In the present talk, we will discuss the SEP spectrum of the $X~1\Sigma g+$ state of acetylene at $\sim 10,000-14,000cm-1$ of energy above the vibrational ground state. Experimental details of the SEP technique will also be given.