Theoretical study on the low-lying excited electronic states and laser cooling feasibility of CuH molecule.

To evaluate the feasibility of the laser cooling of CuH molecule, we investigate the electronic properties, the vibrational and rotational characteristics of the molecule based on the multi-reference configuration interaction method with all-electron basis sets. The potential energy curves (PECs) of X1Σ+, A1Σ+, B1Σ+, a3Σ+, b3Σ+, e3Σ+, C1П, D1П, c3П and d3П states and the transition dipole moments between these states are calculated. The Schrödinger equation of nuclear movement is solved for each electronic state to obtain the rotational and vibration energy levels. The spectroscopic parameters are calculated based on the fitted analytical function from the PECs. The present results are in good agreement with the theoretical and experimental values available in the literature. The optical scheme of the laser cooling for CuH molecule is constructed with A1Σ+ ↔ X1Σ+ as the close-loop transition. Three lasers are necessary in each direction to maintain enough scattering photons because of the limited Franck-Condon factor of 0.78. The wavelengths of the pumping lasers are determined. The recoil temperature is 1.72 μk, which is the expected temperature to be reached through the method of the cooling below the doppler limit.