Analysis of the xylenol isomers by femtosecond laser time of flight mass spectrometry

Xylenol is a phenolic chemical substance having two methyl groups and one hydroxyl group attached to a benzene ring and has six isomers. 2,4-xylenol is the only isomer of the xylenol molecule that is in the liquid phase while the remaining isomers are all in crystal form at room temperature. In the scope of this study, we have experimentally investigated ionization and dissociation properties of xylenol isomers. All experiments were carried out by using a time of flight mass spectrometry (TOF-MS) system coupled with a femtosecond laser system. The laser pulse power-dependent multiphoton ionization of xylenol isomers was investigated by using IR (800 nm) femtosecond laser pulses having a pulse width of ∼90 fs in duration and laser intensities changing from 2.6 × 1013 to 2.6 × 1014 W/cm2. Theoretically, molecular orbitals (LUMO+1, LUMO, HOMO, HOMO–1), vertical and adiabatic ionization energies were calculated using density functional theory (DFT) with B3LYP functional and 6–311++G(d,p) basis set by following geometry optimization and performing conformational analysis.