Study On Excited State Dynamics And Ionic Spectroscopy Of Aromatic Compounds

Excited state dynamics and ionic spectroscopy are the important components of laser chemistry. Study of excited state dynamics and ionic spectroscopy can help us to obtain the information of the excited states and ionic states of the molecules and open a widow to understand the essence of chemical reaction. Femtosecond time-resolved photoelectron imaging has the property of femtosecond time resolution and can real-time investigate the dynamics of molecules which are excited by a femtosecond laser. Mass Analyzed Threshold Ionization Spectroscopy (MATI) is a powerful technique for studies of molecular ions and can offer a very high resolution with mass resolved.Excitedstate dynamics and ionic spectroscopy of several aromatic compounds have been investigated by femtosecond time-resolved photoelectron imaging and mass analyzed threshold spectroscopy. The dissertation is mainly composed of three parts:The first part is the investigation on field-free alignment of asymmetric molecule o-dichlorobenzene in excited states.The excited state dynamics of o-dichlorobenzeneis studied by femtosecond time-resolved photoelectron imaging coupled with femtosecond time-resolved time-of-flight spectrospopy techniques. The lifetime of the first excited state S1of o-dichlorobenzene was determined to be482±10ps. Field-Free alignment of the o-dichlorobenzenein the first excited state S1(with the asymmetry parameter κ=0.153) is realized and rotational wavepacket revival is observed via time-resolved photoelectron angular distributions, which demonstrate the quantum coherent effect between rotation states.The second part is the study on photodissociation dynamics of iodobenzene.The photodissociation dynamics of iodobenzeneis studied by200nm femtosecond laser pulse and a nanosecond laser pulse. The experimental data demonstrate that the pathway of I+is mainly attributed to the dissociation of neutral iodobenzene. However, the pathway of C6H5+is ascribed to the dissociation of iodobenzene cation by nanosecond laser pulse.The third part is two color two-poton MATI spectra of p-methoxystyrene, indene and3,5-difluoroaniline. The accurate adiabatic ionization energiesof cis-p-methoxystyrene, trans-p-methoxystyrene, indene and3,5-difluoroanilineare determined to be62487±5,62512±5,65721±5and65686±5cm-1, respectively. The vibrations in the first excited state (S1) and cation ground state (Do) are assigned with the help of our ab initio and density function theory calculation. The substitution effect on the excited energies and ionization potential values arealso discussed. In addition, the lifetime of p-methoxystyrene and indene in the S1state are investigated using nanosecond time-resolved time-of-flight spectroscopy technique, which demonstrate the effect of different vibrational state on the lifetime of excited state.