Spectroscopy of the simplest Criegee intermediate CH2OO: Simulation of the first bands in its electronic and photoelectron spectra

摘要: CH2OO, the simplest Criegee intermediate, and ozone are isoelectronic. They both play very important roles in atmospheric chemistry. Whilst extensive experimental studies have been made on ozone, there were no direct gas-phase CH2OO until recently when its photoionization spectrum was recorded kinetics of some reactions with a number molecules importance, using mass spectrometry to monitor CH2OO. In order encourage more other intermediates, electronic photoelectron spectra simulated high level structure calculations Franck–Condon factor calculations, results presented here. Adiabatic vertical excitation energies calculated TDDFT, EOM-CCSD, CASSCF methods. Also, DFT, QCISD performed neutral low-lying ionic states, single energy being carried out at higher levels obtain reliable ionization energies. The show that most intense band corresponds equation image1A? ? absorption. It is broad region 250–450?nm showing vibrational modes involving O–O stretching C-O-O bending. Evidence absorption has probably earlier work, albeit low resolution. We suggest prepared this work from reaction CH2I O2 assignment observed solely CH2IOO incorrect. consists two overlapping vibrationally structured bands corresponding one-electron ionizations highest occupied molecular orbitals molecule. each case, adiabatic component these expected be close, 9.971 9.974?eV theory used.