We construct two high order compact schemes for 1D Gross-Pitaevskii (GP) equation. These schemes possess properties of multi-symplectic integrators, splitting method and high order compact method. It improves greatly computational efficiency of multisymplectic integrators. Firstly, 1D GP equation is reformulated into multisymplectic formulation. Then, it is split into a linear multisymplectic Hamiltonian and a nonlinear Hamiltonian system. The nonlinear sub-problem can be solved exactly based on new pointwise mass conservation law. The linear problem is discretized by high order compact multi-symplectic integrator. With different composition of the two sub-problems, we obtain two numerical schemes. These schemes have characters of multisymplectic integrators, splitting method and high order compact schemes, and they are mass-preserving as well. Numerical results are reported to illustrate performance of our methods.

Influence of surface potential barrier on escape probability of gradient-doping negative electron affinity (NEA) GaN photocathode was studied. Electron energy distribution and escape probability are calculated and compared with those of uniform-doping GaN photocathode. It shows that gradient-doping NEA GaN photocathode can obtain higher electron escape probability. And barrier I has an evident influence on escape probability while barrier Ⅱ has limited influence. Photocurrents of two GaN photocathodes are measured with a multi-information-test system. Experimental results show that gradient-doping GaN photocathode has higher escape probability. Obvious effect on escape probability can be found by barrier I from Cs-activation while barrier Ⅱ from Cs/O-joint-activation has little impact.

Electron-impact excitation collision strength Ω(nl-n'l')(3≤n≤7,4≤n'≤7) among configuration-average levels for the Ni-like Ions Pb⁵⁴⁺, Au⁵¹⁺,Ba²⁸⁺,Mo¹⁴⁺,Ge⁴⁺ have been calcuated systematically using the quasirelativitic distorted-wave methods. In addition, the collision strength in high limit have been calculated. The data for the collision strength or thermally averaged rate coefficient over the whole range of energy or temperature have been evaluated by a least-squares spline fitting procedure. As a result, the collision strength with arbitrary electron energy and rate coefficient with arbitrary temperature can be determined by ten parameters.