Dynamics of triplet states in beam-isolated benzaldehyde

Ofer Sneh, Ori Cheshnovsky*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


The radiative and nonradiative dynamics of benzaldehyde in the 0-3750-cm-1 energy interval above the T1 origin were explored. The relative radiative rates were extracted by combining two different simultaneous measurements: laser-induced phosphorescence (LIP) and surface ejection of electrons by laser excited metastables (SEELEM). The ratio of the LIP signal and the SEELEM signal is proportional to the pure radiative rate. The details of the dynamics were rationalized as a development in the coupling of three electronic states. The T1(3nπ*)-T2( 3ππ*) vibronic coupling increases regularly in the region between 400 and ≃2000 cm-1 of excess vibrational energy above the T1 origin. Starting from the excess energy of the S1 origin (1730 cm-1), the S1 excitations are coupled to the sparse T1-T2 background. We have shown that the line profile and dynamics of the S1 manifold in the 1730-2500-cm-1 region can be described in terms of the interaction of an optically active state with a background of almost dark states, in accordance with the theory of radiationless transitions. From our spectroscopic data we have estimated the density of coupled states to be about 200 states/cm-1 and the coupling strength to be 0.05 cm-1. The S1 content in the coupled states is gradually diluted in the 1730-2500-cm-1 region due to the congestion of the triplet states. Finally, the T2 character is eroded probably due to the larger density of T1 states. The T1-T2 and the S1-T1 coupling mechanisms were studied.

Original languageEnglish
Pages (from-to)7154-7164
Number of pages11
JournalJournal of Physical Chemistry
Issue number19
StatePublished - 1991


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