Excited state dynamics of β-carotene explored with dispersed multi-pulse transient absorption

Abstract The excited-state dynamics of β-carotene in hexane was studied with dispersed ultrafast transient absorption techniques. A new excited state is produced after blue-edge excitation. Pump–repump–probe and pump–dump–probe measurements identified and characterized this state, termed S ‡ , which exhibits a blue-shifted spectrum with a longer lifetime than S1. We establish the independent co-existence of the S ‡ and S1 states following the relaxation of S2 and demonstrate that S ‡ is an electronically excited state and not a vibrationally excited ground-state species. Our data support the premise that S ‡ is formed directly from S2 and not via preferential excitation of ground-state sub-populations.

[1]  F. S. Rondonuwu,et al.  A first detection of singlet to triplet conversion from the 11Bu− to the 13Ag state and triplet internal conversion from the 13Ag to the 13Bu state in carotenoids: dependence on the conjugation length , 2003 .

[2]  N. Mataga,et al.  S1 and T1 species of .beta.-carotene generated by direct photoexcitation from the all-trans, 9-cis, 13-cis, and 15-cis isomers as revealed by picosecond transient absorption and transient Raman spectroscopies , 1991 .

[3]  Michael Ottolenghi,et al.  Following evolution of bacteriorhodopsin in its reactive excited state via stimulated emission pumping. , 2002, Journal of the American Chemical Society.

[4]  Ivo H. M. van Stokkum,et al.  Subpicosecond dynamics in the excited state absorption of all-trans-β-carotene , 2002 .

[5]  Klaus Schulten,et al.  The low‐lying electronic excitations in long polyenes: A PPP‐MRD‐CI study , 1986 .

[6]  D. Levy,et al.  Gas-phase photochemistry of the photoactive yellow protein chromophore trans-p-coumaric acid. , 2002, Journal of the American Chemical Society.

[7]  Philip A. Anfinrud,et al.  Pump−Dump−Probe Spectroscopy of Bacteriorhodosin: Evidence for a Near-IR Excited State Absorbance , 1997 .

[8]  Ivo H. M. van Stokkum,et al.  Target Analysis of the Bacteriorhodopsin Photocycle Using a Spectrotemporal Model , 2002 .

[9]  T. Inaba,et al.  Two different pathways of internal conversion in carotenoids depending on the length of the conjugated chain , 2003 .

[10]  Tomáš Polívka,et al.  Dynamics of Excited States of the Carotenoid Peridinin in Polar Solvents: Dependence on Excitation Wavelength, Viscosity, and Temperature. , 2003 .

[11]  H. Frank,et al.  Low-lying electronic states of carotenoids. , 1992, Biochimica et biophysica acta.

[12]  G. Fleming,et al.  An unusual pathway of excitation energy deactivation in carotenoids: Singlet-to-triplet conversion on an ultrafast timescale in a photosynthetic antenna , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[13]  G. Cerullo,et al.  Photosynthetic Light Harvesting by Carotenoids: Detection of an Intermediate Excited State , 2002, Science.

[14]  Ivo H. M. van Stokkum,et al.  Light harvesting by carotenoids incorporated into the B850 light-harvesting complex from Rhodobacter sphaeroides R-26.1: Excited-state relaxation, ultrafast triplet formation, and energy transfer to bacteriochlorophyll , 2003 .

[15]  H. Hashimoto,et al.  Vibrational relaxation of the 2 A g − excited state in all- trans -β-carotene obtained by femtosecond time-resolved Raman spectroscopy , 2001 .

[16]  K. Schulten,et al.  Efficient light harvesting through carotenoids , 2004, Photosynthesis Research.

[17]  J. Jeevarajan,et al.  Optical absorption spectra of dications of carotenoids , 1996 .

[18]  Robin M. Hochstrasser,et al.  Ultrafast Dielectric Response of Proteins from Dynamics Stokes Shifting of Coumarin in Calmodulin , 2000 .

[19]  R. Cogdell,et al.  Carotenoids in Photosynthesis , 1996, Photochemistry and photobiology.

[20]  Sergey A. Kovalenko,et al.  Femtosecond hole-burning spectroscopy with stimulated emission pumping and supercontinuum probing , 1998 .

[21]  Rienk van Grondelle,et al.  An alternative carotenoid-to-bacteriochlorophyll energy transfer pathway in photosynthetic light harvesting , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[22]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[23]  T. Gillbro,et al.  Photophysics and dynamics of the lowest excited singlet state in long substituted polyenes with implications to the very long‐chain limit , 1995 .

[24]  V. Sundström,et al.  Dynamics of vibrational relaxation in the S1 state of carotenoids having 11 conjugated CC bonds , 2002 .

[25]  M. El-Sayed,et al.  The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[26]  M. Mimuro,et al.  Direct Determination of a Lifetime of the S2 State of .beta.-Carotene by Femtosecond Time-Resolved Fluorescence Spectroscopy , 1994 .

[27]  Andrew P. Shreve,et al.  Determination of the S2 lifetime of β-carotene , 1991 .

[28]  Jan Amesz,et al.  Biophysical Techniques in Photosynthesis , 1996, Advances in Photosynthesis and Respiration.