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- https://doi.org/10.1063/1.4975817
Final published version

- Anders Aspegren Sondergaard
- Benjamin Shepperson ,
- Henrik Stapelfeldt

We present an efficient, noise-robust method based on Fourier analysis for reconstructing the threedimensional measure of the alignment degree, <cos(2) theta > directly from its two-dimensional counterpart, <cos(2) theta(2D)> The method applies to nonadiabatic alignment of linear molecules induced by a linearly polarized, nonresonant laser pulse. Our theoretical analysis shows that the Fourier transform of the time-dependent <cos(2)theta(2D)> trace over one molecular rotational period contains additional frequency components compared to the Fourier transform of <cos(2) theta > These additional frequency components can be identified and removed from the Fourier spectrum of <cos(2) theta(2D)> By rescaling of the remaining frequency components, the Fourier spectrum of h <cos(2) theta > is obtained and, finally, <cos(2) theta > is reconstructed through inverse Fourier transformation. The method allows the reconstruction of the <cos(2) theta > trace from a measured <cos(2) theta(2D)> trace, which is the typical observable of many experiments, and thereby provides direct comparison to calculated <cos(2) theta > traces, which is the commonly used alignment metric in theoretical descriptions. We illustrate our method by applying it to the measurement of nonadiabatic alignment of I-2 molecules. In addition, we present an efficient algorithm for calculating the matrix elements of <cos(2)theta(2D)> and any other observable in the symmetric top basis. These matrix elements are required in the rescaling step, and they allow for highly efficient numerical calculation of <cos(2) theta(2D)> and <cos(2) theta > in general.

Original language | English |
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Article number | 013905 |

Journal | Journal of Chemical Physics |

Volume | 147 |

Issue | 1 |

Number of pages | 10 |

ISSN | 0021-9606 |

DOIs | |

Publication status | Published - 7 Jul 2017 |

- ALIGNING MOLECULES, 6J SYMBOLS, FIELDS, PHOTODISSOCIATION, POLARIZATION, DIFFRACTION, PULSES, 3J

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