A Multi-center Distorted-wave Approximation Study On The (E,2e) Process For Some Bio-molecules

Interactions between electrons and atoms or molecules have important connections with physical phenomena in many research fields,such as plasma physics,astro-physics,atmospheric physics,radiation chemistry and biology,involving elastic scattering,ionization,dissociation,excitation,recombination and Charge transfer and many other physical processes.In recent years,experimental studies have shown that sec-ondary particles,especially secondary electrons generated by primary ionization processes,have an important influence on ionizing radiation damage of carbohydrates,water,DNA,and RNA bases.In particular,recent studies have shown that the interaction between low-energy secondary electrons and DNA can lead to DNA single-stranded and double-strand breaks.In order to fully understand the ionizing radiation damage kinetics of these highly complex biomolecules,one possible method is to study electron impact ionization of separated gas phase unit molecules,such as isolated DNA and RNA bases,sugars,and phosphoric acid units.In recent years,the Australian experimental group has conducted a series of electron collision single ionization experiments of biomolecules,including tetrahydrofuran,tetrahydropyran,1,4-dioxane,pyrimidine,phenol,and tetrahydroalditol,etc.In order to understand the influence of structure and kinematics conditions in the process of electron impact ionization,Builth-Williams et al.used the(2,2e)coincidence technique to measure the three structurally similar rings of tetrahydrofuran,tetrahydropyran,and 1,4-dioxane.In their work,the theoretical calculation method was the M3DW method which based on the orientation-averaged molecular orbital approximation in the Madison group,but due to the orientation-averaged molecular orbital approximation,the anisotropic multicenter characteristics of the molecule were neglected,and the theoretical calcula-tion results did not agree with experiments.Our group has recently developed a set of theoretical methods the multi-center distorted-wave method which can well take the multi-center properties of molecules into account.Here we use this method to recalculate the triple differential cross section of tetrahydrofuran,tetrahydropyran and 1,4-dioxane molecules in the electron collision single ionization process under the asymmetric coplanar kinematics conditions.our calculations are compared with the existing experimental data and the results of the Madison group which based on the orientation-averaged molecular orbital approximation to verify the feasibility and applicability of this method to biological molecules.This thesis is divided into the following four parts:The background of this investigation is firstly introduced in Chapter 1.Then some applied theoretical calculation methods are introduced briefly.A multi-center distorted-wave approximation has been introduced in detail in Chapter 2.The general form of the multicenter distorted-wave method,the solution of the ionized electron multi-center continuous wave function,and the ionization transition matrix were introduced in detail.In the third chapter,we use the multi-center distorted-wave method to calculate the triple differential cross section of electron impact single ionization under the asymmetric coplanar kinematics conditions of some biological molecules:tetrahydrofuran,Tetrahydropyran and 1,4-dioxane.And compared with the existing experimental data and the calculation of Madison group which based on the orientation-averaged molecular orbital approximation,our calculation in multi-center distorted-wave method is much better than that of the Madison group.This shows that the multi-center distorted-wave method can be used to calculate the triple differential cross section of larger biomolecules.Finally,in the fourth chapter,the work of this thesis is summarized and prospected.