Prediction Challenge: Simulating Rydberg Photoexcited Cyclobutanone with Surface Hopping Dynamics based on Different Electronic Structure Methods

This research examines the nonadiabatic dynamics of cyclobutanone after excitation into the n-3s Rydberg S2 state. It stems from our contribution to the Special Topic of the Journal of Chemical Physics to test the predictive capability of computational chemistry against unseen experimental data. Decoherence-corrected fewest-switches surface hopping (DC-FSSH) was used to simulate nonadiabatic dynamics with full and approximated nonadiabatic couplings. Several simulation sets were computed with different electronic structure methods, including a multiconfigurational wavefunction (MCSCF) specially built to describe dissociative channels, multireference semiempirical approach, time-dependent density functional theory, algebraic diagrammatic construction, and coupled cluster. MCSCF dynamics predicts a slow deactivation of the S2 state (10 ps), followed by an ultrafast population transfer from S1 to S0 (<100 fs). CO elimination (C3 channel) dominates C2H4 formation (C2 channel). These findings radically differ from the other methods, which predicted S2 lifetimes 10 to 250 times shorter and C2 channel predominance. These results suggest that routine electronic structure methods may hold low predictive power for the outcome of nonadiabatic dynamics.Comment: The main manuscript contains 28 pages with 8 figures. The supplementary material contains 14 pages with 12 figures. In total, the merged pdf document has 42 pages with 20 figure

Weak charge and weak radius of 12{}^{12}C

We present a feasibility study of a simultaneous sub-percent extraction of the weak charge and the weak radius of the ${}^{12}$C nucleus using parity-violating electron scattering, based on a largely model-independent assessment of the uncertainties. The corresponding measurement is considered to be carried out at the future MESA facility in Mainz with $E_{\rm beam} = 155$ MeV. We find that a combination of a $0.3\%$ precise measurement of the parity-violating asymmetry at forward angles with a $10\%$ measurement at backward angles will allow to determine the weak charge and the weak radius of ${}^{12}$C with $0.4\%$ and $0.5\%$ precision, respectively. These values could be improved to $0.3\%$ and $0.2\%$ for a $3\%$ backward measurement. This experimental program will have impact on precision low-energy tests in the electroweak sector and nuclear structure.Comment: 7 pages, 5 figure

Light-Dressing Effect in Laser-Assisted Elastic Electron Scattering by Xe

The light-dressing effect in Xe atoms was identified in laser-assisted elastic electron scattering (LAES) signals. In the angular distribution of LAES signals with energy shifts of ±ℏω recorded by the scattering of 1 keV electrons by Xe in an intense nonresonant laser field, a peak profile appeared at small scattering angles (<0.5°). This peak was interpreted as evidence of the light dressing of Xe atoms induced by an intense laser field on the basis of a numerical simulation in which the light-dressing effect is included.UTokyo Research掲載「光の衣をまとった原子を電子で観る」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/probing-light-dressed-atoms-with-electrons.htmlUTokyo Research "Probing light-dressed atoms with electrons" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/probing-light-dressed-atoms-with-electrons.htm

LDRD project 151362 : low energy electron-photon transport.

At sufficiently high energies, the wavelengths of electrons and photons are short enough to only interact with one atom at time, leading to the popular %E2%80%9Cindependent-atom approximation%E2%80%9D. We attempted to incorporate atomic structure in the generation of cross sections (which embody the modeled physics) to improve transport at lower energies. We document our successes and failures. This was a three-year LDRD project. The core team consisted of a radiation-transport expert, a solid-state physicist, and two DFT experts

Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules

Citation: Wang, X., Le, A. T., Yu, C., Lucchese, R. R., & Lin, C. D. (2016). Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules. Scientific Reports, 6, 11. doi:10.1038/srep23655We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. A simple single-scattering model is proposed and benchmarked to describe the photoionization process and to do the retrieval using a multiple-parameter fitting method