We developed a path imbalance measuring system using a reference interferometer with alterable optical path difference (OPD), aiming to eliminate the uncertainties due to synthetic wavelength measurement and remove the requirement of a known and stable reference OPD in frequency scanning interferometry. The path imbalance can be solved by using the phase ratios between the two interferometers produced before and after altering the OPD in the reference interferometer. The results have shown that the measurement uncertainty and the path imbalance are linearly related and a combined relative uncertainty of 4.9  ×  10−6 (1σ) in path imbalance measurement over a range from 0.5 m to 50 m is achieved. Besides, we analyzed the contributions to the uncertainty that limit the performance of the system, and we discussed how to obtain a better measurement uncertainty.

Laser-modified electron capture processes are studied for the He2++H collision system in the low projectile energy region by solving the time-dependent Schrödinger equation. An obvious enhancement of the total and dominant state-selective charge-transfer cross sections are observed with respect to laser-free and weaker laser cases for low projectile energy. The influence of the laser pulse phase upon the cross sections is also studied and the reduction of the cross section is observed at some pulse phases with the increasing of the projectile energy. The time evolution for the dynamics of the collision system is analyzed in order to explore the dependence of the cross sections upon the pulse phase.