Excited-state absorption and ultrafast relaxation dynamics of protoporphyrin IX and hemin.
The transient evolution of protoporphyrin IX (PPIX) and hemin following the Soret band excitation was measured in the 410-600 nm spectral region with sub-picosecond time resolution. In PPIX the relaxation pathway was characterized in the femto- and picosecond time scale by two processes with time constants of 350 fs and ~6 ps, describing the evolution of the system through internal Q(y) → Q(x) conversion and vibrational relaxation and cooling in the Q(x) state. The lifetime of the Q(x) state was found to be 10.4 ns by time resolved fluorescence measurements. In hemin, the ground state is completely recovered in tens of picoseconds through pathways involving CT and (d,d) states. The experimentally observed vibrational dynamics is mainly due to "hot" ground state transitions.
European Laboratory for Non-Linear Spectroscopy, University of Firenze, Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
Agnese
A
Marcelli
Ivana
I
Jelovica Badovinac
Nada
N
Orlic
Pier Remigio
PR
Salvi
Cristina
C
Gellini
D006427:Hemin / Q000737:chemistry*; D015394:Molecular Structure; D055668:Photochemical Processes; D011524:Protoporphyrins / Q000737:chemistry*; D013816:Thermodynamics
D011524:Protoporphyrins; D006427:Hemin; C028025:protoporphyrin IX