Two-color REMPI (1+1’)+1 of the singlet oxygen 1O2 arising in UV-photodissociation of van der Waals complex C5H8-O2

Photochemistry of the molecular oxygen is important for manifold of atmospheric and photobiological processes. Van der Waals complex of oxygen X-O2 has been shown to be a good model for the study of UV photophysics and photochemistry of the oxygen perturbed by environment 1. The new supramolecular photoprocesses in X-O2 complexes have been revealed. One of them gives rise to the singlet oxygen O2(a1Δg) which is interpreted to be due to supramolecular transition in complex with simultaneous change of the spin of complex partners (double spin-flip) 2: 3(1X–3O2) + hv --> 3(3X–O2(a1Δg)) --> 3X + O2(a1Δg) The singlet oxygen formation was detected with its photodissociation by the same laser pulse with formation of two atoms with specified kinetic energy measured by velocity map imaging technique (VMI). Spectral range of one-laser experiments is limited by wavelength of REMPI of oxygen atoms near 225 nm. Another way to detect the singlet oxygen is REMPI (2+1) itself in spectral range 300- 340 nm 3. In present work the one-laser approach for detection of the singlet oxygen is applied with two color REMPI (1+1’)+1 of singlet oxygen where dye laser radiation (455 - 469 nm) and its second harmonic are used simultaneously. In this approach the same excited intermediate states of O2 have been used. UV-radiation wavelength is within the spectral region of 227-235 nm where photodissociation of the Van der Waals complex of isoprene with oxygen C5H8-O2 is known to give rise to singlet oxygen 2. This approach in combination with VMI has been applied to detect the singlet oxygen arising from van der Waals complex C5H8-O2.