Studies On Hydrogen Atom And H₂～+ In Strong Fields And The Photoionization Cross Section Of Li～+

The atoms and ions in strong fields not only have important applications in as-trophysics, plasma physics and semiconductor physics, but also have great academicalsignificance in many basic questions on atomic physics and quantum mechanics, suchas solving Schr¨odinger equation with inseparable variable, the quantum-classical corre-spondence, and ionization induced by field etc. In this paper, we study the spectra ofthe low-lying hydrogen atom in the parallel electronic and magnetic fields, the resonancestructure of the hydrogen atom and the energies of the hydrogen molecule ion in strongmagnetic fields. Considering the speciality of these questions, we apply di?erent methodsin di?erent systems, including the pseduospectral method, one-center method using B-spline basis and B-spline basis plus the complex coordinate method. The major contentsare as following:(1) We calculate the oscillator strength spectra of the hydrogen atom in parallelmagnetic and electric fields (γ≤1a.u. and F≤10~8V/m) with the psudospectral methodand explain quantitatively the in?uences of additional electric fields on oscillator strengthspectra in the Balmerαseries of the hydrogen atom in magnetic fields using a perturba-tion theory.(2) B-spline basis set plus complex scaling method is applied to calculate exactlythe resonance parameters of hydrogen atom in parallel magnetic and electric fields. Thevarying of the parameter with di?erent magnetic and electric fields is discussed. An interesting phenomenon appears when the magnetic field is increased to some specificalvalue. In some region of the electric field, the widths of states keep invariable. Thereason is still under research. The feasibility of this method extended to calculationof high Rydberg states in cross magnetic and electric fields and multi-electric atomicdouble-excited states in laboratorial field strengths is also discussed.(3) With the advantages of B-spline basis set, we extend the one-center method tothe calculation of equilibrium distances and energies of the ground state and low-lyingstates for hydrogen molecular ion in strong magnetic field. The results show that the one-center method based on B-spline basis is very suitable to calculation of non-symmetricalsystem.(4) We calculate the photoionization cross section of Li~+ with LS coupling interactionby complex scaling method based on B-spline. Comparing to the results in the case ofnon-LS coupling, it adds new spectra of 3P and 3D states, which show that LS couplinginteraction leads to the mixing of single excited states and triple excited states. Thesenew spectra are very small, which means that the LS coupling interaction of Li~+ is verysmall. However, such small cross section is not obtained in present experiment. Withthe development of the laser technology, higher-resolution spectra can be observed, sothat we can study in detail the contribution of smaller coupling, such as the LS couplinginteraction. We hope that our theoretical results can serve as a timely stimulation forfuture experiments.