Spectroscopy, Metastability, and Single and Double Ionization of AlCl

In search of molecular ions for optical cycling: a difficult road

Optical cycling, a continuous photon scattering off atoms or molecules, is the key tool in quantum information science.

Theoretical study of the electronic states of newly detected dications. Case of MgS2+ AND SiN2+

The dications MgS

Laser cooling of the AlCl molecule with a three-electronic-level theoretical model

Feasibility of laser-cooling AlCl molecule is investigated using ab initio quantum chemistry. Potential energy curves, permanent dipole moments, and transition dipole moments for the X(1)Σ(+), a(3)Π, and A(1)Π states are studied based on multi-reference configuration interaction plus Davidson corrections (MRCI+Q) method with ACVQZ basis set, spin-orbit coupling effects are considered at the MRCI+Q level. Highly diagonally distributed Franck-Condon factors (f00 = 0.9988 and f11 = 0.9970) and branching ratios (R00 = 0.9965, R01 = 2.85 × 10(-3), R02 = 6.35 × 10(-4), and R03 = 2.05 × 10(-6)) for the A(1)Π1(ν(')=0)→X(1)Σ0(+) (+)(ν(″)=0) transition are determined. A sufficiently radiative lifetime τ (A(1)Π1) = 4.99 ns is predicted for rapid laser cooling. The proposed cooling wavelength is deep in the ultraviolet region at λ00 = 261.75 nm. Total emission rates for the a(3)Π0(+) →X(1)Σ0(+) (+), a(3)Π1→X(1)Σ0(+) (+), A(1)Π1 → a(3)Π0(+) , and A(1)Π1 → a(3)Π1 transitions are particularly small (∼10 s(-1)-650 s(-1)). The calculated vibrational branching loss ratio to the intermediate a(3)Π0(+) and a(3)Π1 states can be negligible. The results imply the probability of laser cooling AlCl molecule with three-electronic-level.

Quintet electronic states of N2

We use large scale ab initio calculations to investigate the valence and valence-Rydberg quintet states of N(2), their transition moments and their spin-orbit couplings to the close lying triplet electronic states. In addition to the A' (5)Sigma(g)(+) and the C" (5)Pi(ui) states already known, we identify two weakly bound states (2 (5)Sigma(g)(+) and 2 (5)Pi(u)) at approximately 95,300 and 106,200 cm(-1) above N(2)(X (1)Sigma(g)(+), v=0). The other quintets are viewed to be repulsive in nature. Our potentials and couplings are used later to derive a set of accurate spectroscopic data for these quintets, their spin-orbit constants, and to elucidate the quintet-triplet dynamics and the role of these newly identified quintets for the production of cold atomic nitrogen.