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Acta Physica Sinica

The extended “ladder” transition controlled by two harmonic pulses

Niu Ying-Yu, Rong Wang, Qiu Ming-Hui, Jun-Ling Xiu

Published Jan 1, 2016• 0 citations
Publisher

Abstract

The extended “ladder” transition controlled by two harmonic pulses is investigated by using a time-dependent quantum wave packet method. The molecular population transfers from the state|0, 0> angle to the states|5, 0> angle and|5, 2> angle induced by the fundamental and second-harmonic pulses, and to the states|5, 3> angle and |6, 2> angle induced by the fundamental and third-harmonic pulses. The calculated results show that the two harmonic pulses can induce a nearly 100% of population to transfer to the target state. The relative phase of two pulses can affect the population distribution. The variation of population has a period of π for the fundamental and second-harmonic pulses, and a period of 2π for the fundamental and third-harmonic pulses.

DOI
10.7498/aps.65.233301

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The extended “ladder” transition controlled by two harmonic pulses is investigated by using a time-dependent quantum wave packet method. The molecular population transfers from the state|0, 0> angle to the states|5, 0> angle and|5, 2> angle induced by the fundamental and second-harmonic pulses, and to the states|5, 3> angle and |6, 2> angle induced by the fundamental and third-harmonic pulses. The calculated results show that the two harmonic pulses can induce a nearly 100% of population to transfer to the target state. The relative phase of two pulses can affect the population distribution. The variation of population has a period of π for the fundamental and second-harmonic pulses, and a period of 2π for the fundamental and third-harmonic pulses.
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A time-dependent quantum wave-packet method is employed to investigate the rovibrational dynamics of population transfer in the ground electronic state controlled by two-color ($\ensuremath{\omega}+2\ensuremath{\omega}$) pulses analogous to coherently control the processes of ionization and dissociation. The population can be transferred to three target states, $|4,1\ensuremath{\rangle},\phantom{\rule{0.16em}{0ex}}|0,1\ensuremath{\rangle}$, and $|4,0\ensuremath{\rangle}$, at the same time through the ladder $\ensuremath{\Lambda}$ and multiphoton transitions. With the variation of the relative phase between $\ensuremath{\omega}$ and $2\ensuremath{\omega}$ pulses, the population distributions show oscillation behavior with a period of $\ensuremath{\pi}$. The population variation with relative phase depends on the size of the electric field asymmetry. The probabilities transferred to different target states can be controlled by varying the pulse amplitudes.
Abstract The population transfer controlled by fundamental, 2nd-harmonic and 3rd-harmonic pulses is investigated by using the time-dependent quantum wave packet method. By varying the phase ϕ 1 of the fundamental pulse, it can be coherent with the 2nd-harmonic and 3rd-harmonic pulses. Compared with two harmonic pulses, the phase ϕ 1 in three harmonic pulses is more efficient in controlling population transfer. Molecular orientation can be controlled by the phases of the three pulses. The value of molecular orientation mainly depends on the phase coherence between the fundamental and 2nd-harmonic pulses.
Photoassociation via reverse ladder transition controlled by two and four laser pulses is investigated using the time-dependent quantum wave packet method. The calculated results show that the amplitudes of the pulses have an enormous effect on the target population and total yield of association. For the target state with a high energy level, the population of background states can reduce the state-selectivity. Although, the total yield of association is decreased, the four pulses can induce the population transferring to low vibrational levels, and the state-selectivity of the target state is high.
The effect of delay time on photoelectron spectra and state populations of a four-level ladder K 2 molecule is investigated by a pump1–pump2–probe pulse via the time-dependent wave packet approach. The periodical motion of the wave packet leads to the periodical change of the photoelectron spectra. The Autler–Townes triple splitting appears at zero delay time, double splitting appears at nonzero delay time between pump1 and pump2 pulses, and no splitting appears at nonzero delay time between pump2 and probe pulses. The periodical change of the state populations with the delay time may be due to the coupling effect between the two pulses. It is found that the selectivity of the state populations may be attained by regulating the delay time. The results can provide an important basis for realizing the optical control of molecules experimentally.
Abstract We theoretically investigate the complete population transfer among quantum states of the N a 2 molecule using ultrashort pulse trains using the time-dependent wave packet method. The population accumulation of the target state can be steered by controlling the laser parameters, such as the variable pulse pairs, the different pulse widths, the time delays and the repetition period between two contiguous pulses; in particular, the pulse pairs and the pulse widths have a great effect on the population transfer. The calculations show that the ultrashort pulse train is a feasible solution, which can steer the population transfer from the initial state to the target state efficiently with lower peak intensities.