Knowledge Bank

Stimulated emission pumping in conjunction with femtosecond photoelectron spectroscopy has been used to create and monitor a coherent superposition of vibrational levels on the ground $(X~2\Sigma u+)$ state of $I2-$, both $barea$ and clustered with four $CO2$ $moleculesb$. In the bare ion, the resulting wavepacket oscillations were monitored at several excitation energies up to 0.993 eV; energy-dependent frequencies and anharmonicities were extracted which were used to fit the ground state to a modified Morse potential. In the cluster, which was studied with 0.53 eV excitation energy, the rate of energy loss to the $CO2$ molecules was determined both by the increase in the wavepacket oscillation frequency ($3.8cm-1$/ps during the initial three picoseconds of coherence) and by the shift of the measured photoelectron spectrum.