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Articles by John E. Beetar
Different Rise Times of Atomic Br M4,5 3d3/2,5/2 Core Level Absorptions during Br2 C 1Πu 1u State Dissociation via Extreme Ultraviolet Transient Absorption Spectroscopy
Abstract Click to copy section linkSection link copied! The reported “dissociation times” for the Br2 C (1Πu 1u) state by various measurement methods differ widely across the literature (30 to 340 fs). We consider this issue by leveraging attosecond extreme ultraviolet (XUV) transient absorption spectroscopy at the Br M4,5 3d3/2,5/2 edges (66 to 80 eV), tracking core-to-valence (3d → 4p) and core-to-Rydberg (3d → ns, np, n ≥ 5) transitions from the molecular to the atomic limit.
Attosecond Probing of Coherent Vibrational Dynamics in CBr4
Special Issue Published as part of The Journal of Physical Chemistry A special issue “Richard J. Saykally Festschrift”. 1. Introduction Click to copy section linkSection link copied! Preparing and controlling vibrational coherent superposition states (referred to as vibrational wavepackets) in molecules with light is a major theme in light–matter interactions. (1,2) This necessitates control over the creation, detection, and manipulation of the vibrational wavepacket.
Attosecond Probing of Coherent Vibrational Dynamics in CBr4
Special Issue Published as part of The Journal of Physical Chemistry A special issue “Richard J. Saykally Festschrift”. 1. Introduction Click to copy section linkSection link copied! Preparing and controlling vibrational coherent superposition states (referred to as vibrational wavepackets) in molecules with light is a major theme in light–matter interactions. (1,2) This necessitates control over the creation, detection, and manipulation of the vibrational wavepacket.
Light-field synthesizer based on multidimensional solitary states in hollow-core fibers
Abstract Few-cycle, long-wavelength sources for generating isolated attosecond soft x ray pulses typically rely upon complex laser architectures. Here, we demonstrate a comparatively simple setup for generating sub-two-cycle pulses in the short-wave infrared based on multidimensional solitary states in an N2O-filled hollow-core fiber and a two-channel light-field synthesizer.
Thermal effects in molecular gas-filled hollow-core fibers
Abstract Few-cycle sources with high average powers are required for applications to attosecond science. Raman-enhanced spectral broadening of Yb-doped laser amplifiers in molecular gases can yield few-cycle pulses, but thermal excitation of vibrational and rotational degrees of freedom may preclude high-power operation. Here we investigate changes in the spectral broadening associated with repetitive laser interactions in an ${{\rm{N}}_2}{\rm{O}}$-filled hollow-core fiber.
Spectral narrowing broadens applications
Four-wave mixing near atomic resonances offers new opportunities for spectral control of extreme ultraviolet pulses. Fig. 1: Schematic of four-wave mixing process. References 1. Leone, S. R. et al. Nat. Photon. 8, 162–166 (2014). ADS Article Google Scholar 2. Drescher, L. et al. Nat. Photon. https://doi.org/10.1038/s41566-020-00758-8 (2021). 3. Chini, M., Zhao, K. & Chang, Z. Nat. Photon. 8, 178–186 (2014). ADS Article Google Scholar 4. Li, J. et al. Nat. Commun. 8, 186 (2017). ADS Article Google Scholar 5. Gaumnitz, T.
Multioctave supercontinuum generation and frequency conversion based on rotational nonlinearity
Abstract The field of attosecond science was first enabled by nonlinear compression of intense laser pulses to a duration below two optical cycles. Twenty years later, creating such short pulses still requires state-of-the-art few-cycle laser amplifiers to most efficiently exploit “instantaneous” optical nonlinearities in noble gases for spectral broadening and parametric frequency conversion.
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