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

The excited-state dynamics of P-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-double dagger, which exhibits a blue-shifted spectrum with a longer lifetime than S-1. We establish the independent co-existence of the S and S, states following the relaxation of S and demonstrate that S-double dagger is an electronically excited state and not a vibrationally excited ground-state species. Our data support the premise that S-double dagger is formed directly from S-2 and not via preferential excitation of ground-state sub-populations. (C) 2003 Elsevier B.V. All rights reserved.