Laser induced photodissociation of CH2Cl2 and CH2Br2 at 355 nm: an experimental and theoretical study

Experimental and theoretical studies have been carried out for nanosecond 355 nm laser induced dissociation/ionisation of dihalomethanes (CH2Cl2 and CH2Br2) using time of flight mass spectrometer. Both the molecules follow quite similar ionisation pattern and mass spectra showed H+, CH2+, X+, CX+, and CH2X+ as major ions with absence of parent ion peak. The energetics of different dissociation channels in the ground state of CH2X+/CH2X systems was investigated using ab initio calculations. Proposed mechanism involves dissociation of CH2X2 into CH2X, which then dissociates into several distinct competitive channels, products of which are subsequently ionised.