Joint Attosecond Science Laboratory, University of Ottawa and National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.
Phys Rev Lett. 2012 Dec 7;109(23):233904. doi: 10.1103/PhysRevLett.109.233904. Epub 2012 Dec 4.
We bring the methodology of orienting polar molecules together with the phase sensitivity of high harmonic spectroscopy to experimentally compare the phase difference of attosecond bursts of radiation emitted upon electron recollision from different ends of a polar molecule. This phase difference has an impact on harmonics from aligned polar molecules, suppressing emission from the molecules parallel to the driving laser field while favoring the perpendicular ones. For oriented molecules, we measure the amplitude ratio of even to odd harmonics produced when intense light irradiates CO molecules and determine the degree of orientation and the phase difference of attosecond bursts using molecular frame ionization and recombination amplitudes. The sensitivity of the high harmonic spectrum to subtle phase differences in the emitted radiation makes it a detailed probe of polar molecules and will drive major advances in the theory of high harmonic generation.
我们将极性分子的取向方法与高次谐波光谱的相位灵敏度相结合，实验比较了电子从极性分子两端重新复合时产生的阿秒脉冲辐射的相位差。这个相位差会影响到与极性分子排列一致的谐波，抑制与驱动激光场平行的分子发射，而有利于垂直的分子。对于取向分子，我们测量了当强光照在 CO 分子上时产生的偶数到奇数谐波的幅度比，并使用分子框架电离和复合幅度来确定阿秒脉冲的取向程度和相位差。高次谐波光谱对发射辐射中微妙相位差的灵敏度使其成为极性分子的详细探针，并将推动高次谐波产生理论的重大进展。
