Torres Elva A, Lerch Eliza-Beth W, Dai Xingcan, Gilb Stefan, Leone Stephen R
Department of Chemistry, University of California Berkeley, Berkeley, California 94720-1460, USA.
J Chem Phys. 2007 Jan 28;126(4):044310. doi: 10.1063/1.2430525.
Using one color ultrafast pump-probe spectroscopy, the authors create N-level multiphoton rotational wave packets via resonant optical pumping between the A((1)Sigma(u) (+)) and E((1)Sigma(g) (+)) electronically bound states of Li(2) from a single optically state-selected rovibrational state |nu(A)=11, j(A)=28>. The authors find that excitation with a single amplitude shaped femtosecond pulse allows the direct observation of up to a six photon absorption, which generates a coherent superposition of 13 rotational states. The multilevel rotational wave packet is theoretically treated with the multipole moment formalism in order to characterize the experimentally observed time-dependent alignment. In particular, the authors find that the magnetic state distributions measured among coherently excited rotational states generated by the resonant multiphoton pumping reduces the measured coherence amplitudes by as much as 40%.
作者使用单色超快泵浦-探测光谱，通过从单个光学态选择的振转态|ν(A)=11, j(A)=28>在Li₂的A((1)Σ(u)⁺)和E((1)Σ(g)⁺)电子束缚态之间的共振光泵浦，创建了N能级多光子转动波包。作者发现，用单个振幅整形的飞秒脉冲激发能够直接观测到高达六光子吸收，这会产生13个转动态的相干叠加。为了表征实验观测到的随时间变化的取向，使用多极矩形式理论对多能级转动波包进行了理论处理。特别地，作者发现，在由共振多光子泵浦产生的相干激发转动态之间测量的磁态分布，会使测量到的相干振幅降低多达40%。
