Positron-impact Ionization Of Atomic Hydrogen In The Presence Of A Bichromatic Laser Field

We investigate the positron impact-ionization of atomic hydrogen in the presenceof a linearly polarized bichromatic field in the second Born approximation. The tripledifferential cross sections and their dependencies on laser field parameters are discussedand compared with the results modified by a monochromatic field. The thesis consistsof four chapters:In chapter 1, we discuss the basic knowledge about field-free (e,2e)reaction theoryof quantum mechanics and derive the formulas in the first Born approximation andsecond Born approximation.In chapter 2,The laser field is composed of a fundamental componentωand itsharmonic 2ω. With the use of the average excitation energy approximation , the closureapproximation and soft-photon approximation , we derived the laser dressed atom wavefunction as a perturbative solution of the time-dependent schro¨dinger equation in thevelocity gauge. we also derived the Volkov solution of positron in the presence of abichromatic laser field.In chapter 3, The incoming and out going states of positron is described by theVolkov wave functions, and the dressed ground state of target is a first order time-dependent perturbative wavefunction. we study the impact ionizaton of atomic hydro-gen by a positron in the presence of a bichromatic laser field in the first Born approxi-mation. Numerical results for triple differential cross section of multiphoton processesvs difference relative phase ?. We explored the TDCS for difference ejected energiesand compared the photon-sumed TDCS caused by positron and electron.In chapter 4, we study the impact ionizaton of atomic hydrogen by a positron inthe presence of a bichromatic laser field in the second Born approximation. Numericalresults for triple differential cross section of multiphoton processes vs difference laserfield parameters.