Femtosecond stimulated emission pumping:

Abstract

Abstract Femtosecond stimulated emission pumping in conjunction with femtosecond photoelectron spectroscopy is used to monitor dynamics within I2−(CO2)4 following coherent vibrational excitation of the I2− chromophore. Femtosecond pump and dump pulses create an I2− wavepacket with 0.53 eV vibrational energy. Subsequent evolution of this wavepacket is monitored via its time-dependent photoelectron spectrum. At this energy, the vibrational frequency of the embedded I2− is 80 cm−1, 7 cm−1 higher than that of bare I2−. As the I2− loses energy to the CO2 molecules, the wavepacket frequency increases linearly at a rate of 3.8 cm−1/ps during the initial 3 ps of coherence. The rate of energy transfer can be determined either by this increase in vibrational frequency or by the shift of the measured photoelectron spectrum. No solvent evaporation during the first 7 ps is observed, but three CO2 molecules evaporate on a microsecond time scale.