Ultrafast Nonradiative Relaxation Channels of Tryptophan.
The nonradiative relaxation channels of gas-phase tryptophan excited along the S1-S4 excited states (287-217 nm) have been tracked by femtosecond time-resolved ionization. In the low-energy region, λ ≥ 240 nm, the measured transient signals reflect nonadiabatic interactions between the two bright La and Lb states of ππ* character and the dark dissociative πσ* state of the indole NH. The observed dynamical behavior is interpreted in terms of the ultrafast conversion of the prepared La state, which simultaneously populates the fluorescent Lb> and the dissociative πσ* states. At higher energies, after excitation of the S4 state, the tryptophan dynamics diverges from that observed in indole, pointing to the opening of a relaxation channel that could involve states of the amino acid part. The work provides a detailed picture of the processes and electronic states involved in the relaxation of the molecule, after photoexcitation in the near part of its UV absorption spectrum.
Departamento de Quı́mica-Fı́sica, Facultad de Ciencia y Tecnologı́a, Universidad del Paı́s Vasco (UPV/EHU). Apart. 644, 48080 Bilbao, Spain.
Virginia
V
Ovejas
Departamento de Quı́mica-Fı́sica, Facultad de Ciencia y Tecnologı́a, Universidad del Paı́s Vasco (UPV/EHU). Apart. 644, 48080 Bilbao, Spain.
Marta
M
Fernández-Fernández
Departamento de Quı́mica-Fı́sica, Facultad de Ciencia y Tecnologı́a, Universidad del Paı́s Vasco (UPV/EHU). Apart. 644, 48080 Bilbao, Spain.
Raúl
R
Montero
Departamento de Quı́mica-Fı́sica, Facultad de Ciencia y Tecnologı́a, Universidad del Paı́s Vasco (UPV/EHU). Apart. 644, 48080 Bilbao, Spain.
Fernando
F
Castaño
Departamento de Quı́mica-Fı́sica, Facultad de Ciencia y Tecnologı́a, Universidad del Paı́s Vasco (UPV/EHU). Apart. 644, 48080 Bilbao, Spain.
Asier
A
Longarte
dynamics; femtosecond; nonadiabatic; nonradiative; photochemistry; photophysics; relaxation