Rotational Coherence Encoded in an “Air-Laser” Spectrum of Nitrogen Molecular Ions in an Intense Laser Field

• Main Authors: Haisu Zhang, Chenrui Jing, Jinping Yao, Guihua Li, Bin Zeng, Wei Chu, Jielei Ni, Hongqiang Xie, Huailiang Xu, See Leang Chin, Kaoru Yamanouchi, Ya Cheng, Zhizhan Xu
• Format: Article
• Language: English
• Published: American Physical Society 2013-10-01
• Series: Physical Review X
• Online Access: http://doi.org/10.1103/PhysRevX.3.041009
• ISSN: 2160-3308

We investigate lasing action in aligned nitrogen molecular ions (N_{2}^{+}) produced in an intense laser field. We find that, besides the population inversion between the B^{2}Σ_{u}^{+}-X^{2}Σ_{g}^{+} states, which is responsible for the observed simulated amplification of a seed pulse, a rotational wave packet in the ground vibrational state (v=0) of the excited electronic B^{2}Σ_{u}^{+} state has been created in N_{2}^{+}. The rotational coherence can faithfully encode its characteristics into the amplified seed pulses, enabling reconstruction of rotational wave packets of molecules in a single-shot detection manner from the frequency-resolved laser spectrum. Our results suggest that the air laser can potentially provide a promising tool for remote characterization of coherent molecular rotational wave packets.