Impulsive rotational Raman scattering of N2 by a remote "air laser" in   femtosecond laser filament
  We report on experimental realization of impulsive rotational Raman scattering from neutral nitrogen molecules in a femtosecond laser filament using an intense self-induced white-light seeding "air laser" generated during the filamentation of an 800 nm Ti: Sapphire laser in nitrogen gas. The impulsive rotational Raman fingerprint signals are observed with a maximum conversion efficiency of ~0.8%. Our observation provides a promising way of remote identification and location of chemical species in atmosphere by rotational Raman scattering of molecules. 
Jielei Ni, Wei Chu, Haisu Zhang, Bin Zeng, Jinping Yao, Guihua Li,   Chenrui Jing, Hongqiang Xie, Huailiang Xu, Ya Cheng, an...
physics.optics