Vibrational ladder climbing in NO by ultrashort infrared laser pulses

The anharmonic vibrational ladder of nitric oxide (NO) is climbed by irradiating the molecule with femtosecond infrared (IR) pulses. The free-electron laser FELIX is tuned to l = 5.3 µm with a bandwidth of D l = 0.3 µm, corresponding to a pulse duration of 150 femtoseconds. Transfer to the excited states of NO is monitored by 1 + 1 REMPI. Population is found up to v’ = 5, the highest level within reach of the IR bandwidth. The average transfer per step of the ladder is found to be 17%.