AUTHOR=Zhang Rong , Hu Jin-Wei , Han Yong-Chang , Fu Bina , Shundalau Maksim 

TITLE=Steering thermal photoassociation of magnesium atoms by two time-delayed femtosecond laser pulses

JOURNAL=Frontiers in Physics

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2023.1114719

DOI=10.3389/fphy.2023.1114719

ISSN=2296-424X

ABSTRACT=<p>By solving the full-dimensional time-dependent Schrödinger equation with the thermal-random-phase wavepacket method, we investigate the photoassociation (PA) process of hot (1000 K) magnesium atoms induced by two time-delayed femtosecond laser pulses. Driven by the 840 nm fs laser pulses, the Mg<sub>2</sub> molecules can be formed on the four excited states, (1)<sup>1</sup>Π<sub><italic>g</italic></sub>, (1)<sup>1</sup>Π<sub><italic>u</italic></sub>, (2)<sup>1</sup>Π<sub><italic>u</italic></sub>, and <inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mn>1</mml:mn></mml:mrow></mml:msup><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">Σ</mml:mi></mml:mrow><mml:mrow><mml:mi>u</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>, from the initial electronic ground state <inline-formula id="inf2"><mml:math id="m2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mi>X</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn></mml:mrow></mml:msup><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">Σ</mml:mi></mml:mrow><mml:mrow><mml:mi>g</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>. It is found that the three-photon couplings between <inline-formula id="inf3"><mml:math id="m3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mi>X</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn></mml:mrow></mml:msup><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">Σ</mml:mi></mml:mrow><mml:mrow><mml:mi>g</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> and the three ungerade states [(1)<sup>1</sup>Π<sub><italic>u</italic></sub> (2)<sup>1</sup>Π<sub><italic>u</italic></sub>, and <inline-formula id="inf4"><mml:math id="m4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mn>1</mml:mn></mml:mrow></mml:msup><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">Σ</mml:mi></mml:mrow><mml:mrow><mml:mi>u</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>], play dominant roles in the population transfer process. By scanning the pulse duration <italic>τ</italic> from 50 to 200 fs, and varying the delay time <italic>δt</italic><sub>0</sub> from 0 to 2<italic>τ</italic> fs, we find that the final PA population is strongly dependent on the two parameters. For a given <italic>δt</italic><sub>0</sub>, the parameter <italic>τ</italic> can induce a significant variation (2 ∼ 6.8 times) for the final PA population transfer, and for a given <italic>τ</italic>, one can also obtain a significant variation (2.7 ∼ 3.5 times) of the final PA population by varying <italic>δt</italic><sub>0</sub>. Additionally, the dynamics of the coherently vibrational wavepackets of the four excited states are also influenced by the two parameters.</p>