;Emission spectra following the photolysis of bromomethanes (CBr4, CHBr3, CHBr2Cl, CHBrCl2, and CH2Br2) at different ultraviolet wavelengths were recorded at ambient temperature for investigating the formation mechanisms of highly excited atomic bromine. This work improved the experimental conditions to obtain better signal-to-noise ratios in the emission spectra, and several newly observed transitions of atomic bromine were found. Power dependence and pressure dependence measurements were also conducted. The results indicate that the formation mechanism of highly excited atomic bromine is a four-photon process instead of a three-photon process reported in the previous study. For these bromomethanes, the photolysis wavelength dependences were acquired and show a similar decreasing trend from 266 nm to 300 nm. This photolysis wavelength dependence is profoundly different from that of iodomethanes. Based on the reaction enthalpies and related photoelectron spectra, the most likely mechanism for the formation of highly excited bromine is a 1+3 process.
