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arXiv · 1606.01622

Nonlinear two-dimensional terahertz photon echo and rotational spectroscopy in the gas phase

Jian Lu·Yaqing Zhang·Harold Y. Hwang·Benjamin K. Ofori-Okai·Sharly Fleischer·Keith A. Nelson
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Abstract

Ultrafast two-dimensional spectroscopy utilizes correlated multiple light-matter interactions for retrieving dynamic features that may otherwise be hidden under the linear spectrum. Its extension to the terahertz regime of the electromagnetic spectrum, where a rich variety of material degrees of freedom reside, remains an experimental challenge. Here we report ultrafast two-dimensional terahertz spectroscopy of gas-phase molecular rotors at room temperature. Using time-delayed terahertz pulse pairs, we observe photon echoes and other nonlinear signals resulting from molecular dipole orientation induced by three terahertz field-dipole interactions. The nonlinear time-domain orientation signals are mapped into the frequency domain in two-dimensional rotational spectra which reveal J-state-resolved nonlinear rotational dynamics. The approach enables direct observation of correlated rotational transitions and may reveal rotational coupling and relaxation pathways in the ground electronic and vibrational state.

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Jian Lu, Yaqing Zhang, Harold Y. Hwang, Benjamin K. Ofori-Okai, Sharly Fleischer, Keith A. Nelson. 2016-06-06. Nonlinear two-dimensional terahertz photon echo and rotational spectroscopy in the gas phase. https://doi.org/10.1073/pnas.1609558113

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