Few-Femtosecond C2H4 + Internal Relaxation Dynamics Accessed by Selective Excitation

• Published in: The journal of physical chemistry letters Vol. 13; no. 48; pp. 11169 - 11175
• Main Authors: Lucchini, Matteo, Mignolet, Benoit, Murari, Mario, Gonçalves, Cayo E. M., Lucarelli, Giacinto D., Frassetto, Fabio, Poletto, Luca, Remacle, Françoise, Nisoli, Mauro
• Format: Journal Article Web Resource
• Language: English
• Published: American Chemical Society 08.12.2022; American Chemical Society (ACS)
• Subjects: Chemistry; Chimie; General Materials Science; Letter; Physical and Theoretical Chemistry; Physical Insights into Light Interacting with Matter; Physical, chemical, mathematical & earth Sciences; Physique, chimie, mathématiques & sciences de la terre
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.2c02763

Dissociation of the ethylene cation is a prototypical multistep pathway in which the exact mechanisms leading to internal energy conversions are not fully known. For example, it is still unclear how the energy is exactly redistributed among the internal modes and which step is rate-determining. Here we use few-femtosecond extreme-ultraviolet pulses of tunable energy to excite a different superposition of the four lowest states of C2H4 + and probe the subsequent fast relaxation with a short infrared pulse. Our results demonstrate that the infrared pulse photoexcites the cationic ground state (GS) to higher excited states, producing a hot GS upon relaxation, which enhances the fragmentation yield. As the photoexcitation probability of the GS strongly depends on the molecular geometry, the probing by the IR pulse provides information about the ultrafast excited-state dynamics and the type of conical intersection (planar or twisted) involved in the first 20 fs of the nonradiative relaxation.