Ultrafast dynamics of pyridine in “channel three” region

The ultrafast dynamics of the S1 (nπ*) state of pyridine has been investigated by using femtosecond time-resolved mass spectrometry and photoelectron imaging combined with (1 + 2′) resonance-enhanced multiphoton ionization via the Rydberg states. Upon excitation into the channel-three region, an ultrafast decay process is observed with a lifetime of about 3.7 ps. The fragment ions show an additional ultrafast decay component. Time resolved photoelectron imaging experiments reveal the excited pyridine in channel three region relaxes to an optically dark state on this short time scale. According to previous experimental and theoretical results, we suggest tentatively the ultrafast channel is due to IVR induced fast internal conversion.

Graphical abstractTime-resolved photoelectron images (inverse-Abel transform) of pyridine taken at different pump–probe delay times. Femtosecond pump laser at 271.5 nm excites the molecules into the S1 state above the channel-three threshold. The time evolution of the prepared state is ionized by a delayed probe laser (407.1 nm).Figure optionsDownload full-size imageDownload as PowerPoint slide