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Field-free orientation of molecules
1Department of Computational Science, The National University of Singapore, Singapore, Singapore 119260.
Physical Review Letters
|November 3, 2001
Summary
Linear polar molecules can be controllably oriented using terahertz half-cycle pulses. This creates a rotational wave packet, leading to field-free, time-dependent molecular orientation, demonstrated computationally for LiH and NaI.
Area of Science:
- Quantum dynamics
- Molecular physics
- Physical chemistry
Background:
- Linear polar molecules possess rotational states.
- Terahertz (THz) electromagnetic pulses can interact with molecular rotational levels.
Purpose of the Study:
- To investigate the impulsive excitation of linear polar molecules using THz half-cycle pulses.
- To demonstrate the creation of rotational wave packets and subsequent molecular orientation.
Main Methods:
- Simulating the interaction of a linear polar molecule with a half-cycle pulse.
- Utilizing quantum mechanics to model the time evolution of rotational states.
- Computational demonstration at finite temperatures.
Main Results:
- Impulsive excitation generates rotational wave packets with mixed parity states.
- The wave packet evolution leads to alternating molecular orientations.
- Field-free, time-dependent orientation was computationally verified.
Conclusions:
- THz half-cycle pulses can induce controllable, time-dependent molecular orientation.
- This phenomenon is observable in molecules like LiH and NaI.
- The findings have implications for controlling molecular dynamics.