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Quantifying rival bond fission probabilities following photoexcitation: C-S bond fission in t-butylmethylsulfide.

Matthew BainChristopher S HansenTolga N V KarsiliMichael N R Ashfold
Published in: Chemical science (2019)
We illustrate a new, collision-free experimental strategy that allows determination of the absolute probabilities of rival bond fission processes in a photoexcited molecule - here t-butylmethylsulfide (BSM). The method combines single photon ('universal') ionization laser probe methods, simultaneous imaging of all probed fragments (multi-mass ion imaging) and the use of an appropriate internal calibrant (here dimethylsulfide). Image analysis allows quantification of the dynamics of the rival B-SM and BS-M bond fission processes following ultraviolet (UV) excitation of BSM and shows the former to be twice as probable, despite the only modest (∼2%) differences in the respective ground state equilibrium C-S bond lengths or bond strengths. Rationalising this finding should provide a stringent test of the two close-lying, coupled excited states of 1A'' symmetry accessed by UV excitation in BSM and related thioethers, of the respective transition dipole moment surfaces, and of the geometry dependent non-adiabatic couplings that enable the rival C-S bond fissions.
Keyphrases
  • high resolution
  • transition metal
  • electron transfer
  • molecular dynamics simulations
  • energy transfer
  • photodynamic therapy
  • living cells
  • molecularly imprinted
  • liquid chromatography