Detection of the time variance of the mass ratio of electron to proton

We have proposed the precise measurement of vibrational transition in the ground electronic state of CaH+ for the test of the temporal change of the mass ratio of electron to proton. We have carried out ab initio calculations of Ca+-H pair potential to evaluate the transition frequency and intensity of the CaH+ in the several low lying states. We have employed the laser ablation of Ca metal in the hydrogen gas to produce CaH+ containing plasma and measured several bands of absorption lines. Although most of them were assigned to the transitions of neutral CaH, several bands have been left to be assigned, and might contain the CaH+ transitions. We have also developed a Stark guide of neutral polar molecules to introduce cold molecule into the ion trap and to produce cold CaH+. Several molecules (ND3, NH3, CH3OH, and CH3F) have been guided and their velocity distributions have been measured. By lowering the nozzle temperature down to 210K, molecular flux has been increased up to twice.