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Issue 36, 2017
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Theoretical investigation on spin-forbidden cooling transitions of gallium hydride

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Herein, the spin-forbidden cooling of a gallium hydride molecule is investigated using ab initio quantum chemistry. The cooling transition and the corresponding potential energy curves including Image ID:c7cp02295f-t1.gif, a3Π0, a3Π0+, a3Π1, a3Π2, A1Π1, Image ID:c7cp02295f-t2.gif, 13Σ+1, Image ID:c7cp02295f-t3.gif, Image ID:c7cp02295f-t4.gif, and 23Σ+1 states are simulated based on the multi-reference configuration interaction approach plus Davidson corrections method. By solving the nuclear Schrödinger equation, we calculate the spectroscopic constants of these states, which are in good agreement with the available experimental values. Based on the transition data, there seems to be a theoretical puzzle: highly diagonally distributed Franck–Condon factor f00 for transitions Image ID:c7cp02295f-t5.gif, Image ID:c7cp02295f-t6.gif, and Image ID:c7cp02295f-t7.gif for the gallium hydride molecule but the intervening state A1Π1 for Image ID:c7cp02295f-t8.gif transition is prohibitive to laser cooling. In addition, the Image ID:c7cp02295f-t11.gif transition does not have a suitable rate of optical cycling owing to a large radiative lifetime for Image ID:c7cp02295f-t12.gif state. Our theoretical simulation indicates the solution to the puzzle: the Image ID:c7cp02295f-t9.gif transition has a high emission rate, and there is a suitable radiative lifetime for a3Π1 state, which can ensure rapid and efficient laser cooling of gallium hydride. The proposed laser drives Image ID:c7cp02295f-t13.gif transition by using three wavelengths (main pump laser λ00; two repumping lasers λ10 and λ21). These results demonstrate the possibility of laser-cooling the gallium hydride molecule, and a sub-microkelvin cool temperature can be reached for this molecule.

Graphical abstract: Theoretical investigation on spin-forbidden cooling transitions of gallium hydride

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Publication details

The article was received on 10 Apr 2017, accepted on 15 Aug 2017 and first published on 16 Aug 2017

Article type: Paper
DOI: 10.1039/C7CP02295F
Citation: Phys. Chem. Chem. Phys., 2017,19, 24647-24655
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    Theoretical investigation on spin-forbidden cooling transitions of gallium hydride

    Y. Zhang, H. Zhang, H. Song, Y. Yu and M. Wan, Phys. Chem. Chem. Phys., 2017, 19, 24647
    DOI: 10.1039/C7CP02295F

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