Direct observation of electronic relaxation dynamics in adenine via time-resolved photoelectron spectroscopy.
We present femtosecond time-resolved photoelectron spectra of adenine in a molecular beam, recorded at pump wavelengths of 250, 267, and 277 nm. This leads to initial excitation of the bright S2(pipi*). Close to the band origin (277 nm), the lifetime is several picoseconds. Higher vibronic levels (267 and 250 nm excitation) show much shorter lifetimes of t < 50 fs, and we observe strong coupling between S2(pipi*) and S1(npi*). Rapid internal conversion (t < 50 fs) populates the lower lying S1(npi*) state which has a lifetime of 750 fs. At 267 nm, we found evidence for an additional channel which is consistent with the dissociative S3(pisigma*) state, previously proposed as an ultrafast relaxation pathway from S2(pipi*).
Ullrich
Susanne
S
Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, Canada K1A 0R6.
Schultz
Thomas
T
Zgierski
Marek Z
MZ
Stolow
Albert
A
D000225:Adenine / Q000737:chemistry*; D004583:Electrons; D013057:Spectrum Analysis / Q000379:methods*
D000225:Adenine