1,2,3,4,5-Pentamethyl-cyclopentadiene dynamics probed by photoionization

PHYS 343

Fedor Rudakov, fedor_rudakov@brown.edu and Peter M. Weber, peter_weber@brown.edu. Department of Chemistry, Brown University, 324 Brook St, Providence, RI 02912
1,2,3,4,5-pentamethyl-cyclopentadiene has, upon excitation of the 1B2 state at 4.65 eV, an ultrafast curve crossing dynamics that returns the molecule to the ground state via the 2A1 state. Using time-resolved mass spectrometry and photoelectron spectroscopy we observed the 1,2,3,4,5-pentamethyl-cyclopentadiene relaxation and obtained time constants of 182(32) fs and 60(26) fs, respectively, for the curve crossings. Upon reaching the ground state surface, the molecule has ample energy to form isomers. Our experiments show conclusively, however, that no measurable structural changes take place on a femtosecond or picosecond timescale.