Controlling population of the molecular rotational state and the alignment theoretically by tailored femtosecond laser pulse.

Yunxia Huang,Shuwu Xu

doi:10.1098/rsos.171502

Abstract

We demonstrate that the population of the molecular rotational state through a stimulated impulsive Raman excitation can be controlled by tailoring the femtosecond laser pulse with a V-style phase modulation. The results show that, by precisely manipulating the modulation parameters, both the odd and even populations of the molecular rotational state can be completely suppressed or reconstructed. Meanwhile, the relative excitation between the odd and even populations can be obtained. Finally, we show that field-free molecular alignment can be controlled due to the modulation of the molecular rotational state populations.

Highlights

Quantum coherent control has attracted considerable attention in the past decades due to its ability to steer a quantum system towards a desired outcome by the light–matter interaction [1,2,3,4,5]
We demonstrate that the populations of the molecular rotational state through a stimulated impulsive Raman excitation can be controlled by tailoring the femtosecond laser pulse with a V-style phase modulation
To further clearly observe the manipulations of the spectral phase modulation to the transition probabilities, we present Podd, Peven and P as a function of the modulation depth τ with the modulation position δω = 0, and the result is shown in figure 3

Summary

Introduction

Quantum coherent control has attracted considerable attention in the past decades due to its ability to steer a quantum system towards a desired outcome by the light–matter interaction [1,2,3,4,5]. Pulse shaping techniques have been notably applied to exercise control on the ground state molecular 2 populations. The reason is that the temporal evolution of the rotational wave packets can lead to the macroscopic molecular alignment or orientation along the laser polarization [17,18,19,20]. We demonstrate that the populations of the molecular rotational state through a stimulated impulsive Raman excitation can be controlled by tailoring the femtosecond laser pulse with a V-style phase modulation. The contributions of the relative even and odd rotational states populations to the rotational wave packet can be manipulated and, the field-free molecular alignment

Theory

Results and discussions

Conclusion