Femtosecond pump-supercontinuum probe and transient lens spectroscopy of adonixanthin.
The ultrafast internal conversion (IC) dynamics of adonixanthin in organic solvents were studied by pump-supercontinuum probe (PSCP) and transient lens (TL) spectroscopy after photoexcitation to the S(2) state. Transient PSCP spectra in the range 344-768 nm provided the spectral evolution of the S(0)-->S(2) ground state bleach and S(1)-->S(n) excited state absorption. Time constants were tau(2) =115 and 111 fs for the S(2)-->S(1) IC and tau(1)=6.4 and 5.8 ps for the S(1)-->S(0) IC in acetone and methanol, respectively. There was only an insignificant polarity dependence of tau(1), underlining the negligible importance of intramolecular charge transfer (ICT) in the lowest-lying excited state of C(40) carotenoids with carbonyl substitution on the beta-ionone ring. A blueshift and a spectral narrowing of the S(1)-->S(n) ESA band, likely due to solvation dynamics, and formation of the adonixanthin radial cation at high pump energies via resonant two-photon ionization were found.
Lenzer
Thomas
T
Georg-August-Universität Göttingen, Institut für Physikalische Chemie, Tammannstrasse 6, 37077 Göttingen, Germany.
Schubert
Steffen
S
Ehlers
Florian
F
Lohse
Peter W
PW
Scholz
Mirko
M
Oum
Kawon
K
D002338:Carotenoids / Q000737:chemistry*; D015335:Molecular Probes; D013057:Spectrum Analysis / Q000379:methods*
D015335:Molecular Probes; D002338:Carotenoids; C539602:adonixanthin