| Abstract: | Ultrafast dissociation dynamics of chloroiodomethane(CH_2ICl)in the B band is studied by femtosecond timeresolved time-of-flight(TOF)mass spectrometry.Time-resolved TOF mass signal of parent ion(CH_2ICl~+)and main daughter ion(CH_2 Cl~+)are obtained.The curve for the transient signal of CH_2ICl~+ is simple and can be well fitted by an exponential decay convoluted with a Gaussian function.The decay constant determined to be less than 35 fs reflects the lifetime of the B band.Significant substituent effects on photodissociation dynamics of CH_2ICl compared with CH3I are discussed.The dissociation time from the parent ion CH_2ICl~+ to the daughter ion CH_2 Cl~+ is determined in the experiment.The optimized geometry of the ionic state of CH_2ICl and the ionization energy are calculated for further analysis of the measurements.In addition,compared with the parent ion,a new decay component with time constant of ~596 fs is observed for CH_2 Cl~+,and reasonable mechanisms are proposed for the explanation. |
