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Recently, several laser techniques have been suggested and demonstrated efficient control over molecular rotation and orientation in space. The ëoptical centrifugeí[1], ëoptical propellerí[2-4], and ëchiral pulse trainí[5] have been successful in using lasers to excite a fast unidirectional molecular spinning. Rotational energy of such molecules exceeds considerably their translational energy, which justifies calling them ìmolecular super-rotorsî.
We analyze interaction of a non-resonant circularly polarized laser pulse with a gas of fast spinning molecules. It is shown that due to the exchange of angular momentum and energy between the pulse and the medium, the probe light inverts its polarization handedness and experiences a frequency shift controllable by the sense and the rate of molecular rotation. The phenomenon appears due to the fast- rotating optical birefringence of the medium, and is related to the so called angular Doppler effect[6] that was observed in the past with optical elements mechanically rotating at about 100 Hz. In our implementation, however, the rotational Doppler shift is found to reach the level of several THz. The analysis is based on the coupled polarization modes approach treated in the paraxial approximation, and combined with dynamics of the rotational wave packets at thermal conditions. Our theory is supported by two recent experiments performed at the Weizmann Institute[7] and UBC[8], and it provides a good qualitative and quantitative description of the experimental observations. We also consider collisional dynamics in a gas of laser-excited molecular super-rotors, and demonstrate theoretically inhibited rotational-translational (RT) relaxation, anisotropic diffusion, and explosive RT energy exchange.
References:
1. J. Karczmarek, J. Wright, P. Corkum and M. Ivanov, Physical Review Letters 82 (17), 3420-3423 (1999).
2. S. Fleischer, Y. Khodorkovsky, Y. Prior and I. Sh. Averbukh, New Journal of Physics 11, 15 (2009).
3. K. Kitano, H. Hasegawa and Y. Ohshima, Physical Review Letters 103 (22), 223002 (2009).
4. Y. Khodorkovsky, K. Kitano, H. Hasegawa, Y. Ohshima, and I. Sh. Averbukh, Physical Review A 83, 023423 (2011).
5. S. Zhdanovich, A. A. Milner, C. Bloomquist, J. Flofl, I.Sh. Averbukh, J. W. Hepburn, and V. Milner,
Phys. Rev.Lett. 107, 243004 (2011).
6. B. A. Garetz, J. Opt. Soc. Am. 71 (5), 609-611 (1981).
7. O. Korech, U. Steinitz, R. J. Gordon, I. Sh. Averbukh and Y. Prior, Nature Photonics 7, 711 (2013).
8. A. Korobenko, A. A. Milner and V. Milner, arXiv:1304.0438 (2013).
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