Education

• PhD, University of Rochester, New York, USA
• BSc, Louisiana State University, Louisiana, USA

Current Projects

We aim to understand the fundamental x-ray interaction with atoms, molecules and clusters and the applications of intense x-ray pulses.

• Atoms in Intense X-ray Pulses:

We have developed a new Monte Carlo rate equation (MCRE) approach that includes resonance transitions, in addition to the usual photoionization, Auger decay and fluorescence processes.  This approach tracks transient electron dynamics and identifies ​“hot spots” for enhanced x-ray ionization in heavy elements exposed to intense, short pulses .

• Single-particle-Imaging with Intense X-ray Pulses

We devised Monte-Carlo/Molecular-Dynamics (MC/MD) computational model to obtain an atomistic view of the dynamical x-ray induced electronic processes and the subsequent nuclear dynamics within the target system throughout the x-ray pulse. This approach allows study of the correlation of sample absorption and scattering response in complex systems and the resolution limit of single-particle-imaging technique.  Our codes are highly parallelized and have been used to perform calculations for up to 50 million particles using high-performance computers at Argonne Leadership Computing Facility.

• X-ray Fluorescence of Nanosized Systems in XFEL Pulses

We are currently exploring intensity correlations from fluorescence spectrum of complex system for high-resolution structural imaging.  Recently, we studied the fluorescence processes of nanosized systems exposed to intense XFEL pulse and found that the ultrafast transient electronic processes and dense electron environment produce x-ray emission profiles in an extended sample that are very different from the atomic profile and additional fluorescence pathways.

Selected Publications

• Phay J Ho, Christopher Knight, Linda Young, ​“Fluorescence intensity correlation imaging with high spatial resolution and elemental contrast using intense x-ray pulses,” Structural Dynamics 8, 044101(2021).
• Adam E. A. Fouda, Phay J. Ho, ​“Site-specific generation of excited state wavepackets with high-intensity attosecond x rays,” J. Chem. Phys. 154 (22), 224111 (2021).
• Chelsea E Liekhus-Schmaltz, Phay J Ho, Robert B Weakly, Andrew Aquila, Robert W Schoenlein, Munira Khalil, Niranjan Govind, ​“Ultrafast x-ray pump x-ray probe transient absorption spectroscopy: A computational study and proposed experiment probing core-valence electronic correlations in solvated complexes,” J. Chem. Phys. 154, 214107 (2021).
• Phay J Ho, Adam EA Fouda, Kai Li, Gilles Doumy, Linda Young, ​“Ultraintense, ultrashort pulse x-ray scattering in small molecules,” Faraday Discussions on Time-resolved imaging of photoiniduced dynamics, 228, 139 (2020).
• Kai Li, Marie Labeye, Phay J Ho, Mette B Gaarde, Linda Young, ​“Resonant propagation of x rays from the linear to the nonlinear régime,” Physical Review A 102, 053113 (2020).
• A.E.A. Fouda, P.J. Ho, R.W. Dunford, E.P. Kanter, B. Krassig, L. Young, E.R. Peterson, E.C. Landahl, L. Pan, D.R. Beck, S.H. Southworth, ​“Resonant x-ray absorption of strong-field-ionized CF3Br,” J. Phys. B: At. Mol. Opt. Phys. 53, 244009 (2020).
• Phay J Ho, Christopher Knight, Linda Young, ​“Extended x-ray emission times of clusters in intense x-ray pulses,” Physical Review A 101, 043413 (2020).
• Jordan T O’Neal, Elio G Champenois, Solene Oberli, Razib Obaid, Andre Al-Haddad, Jonathan Barnard, Nora Berrah, Ryan Coffee, Joseph Duris, Gediminas Galinis, Douglas Garratt, James M Glownia, Daniel Haxton, Phay Ho, Siqi Li, Xiang Li, James MacArthur, Jon P Marangos, Adi Natan, Niranjan Shivaram, Daniel S Slaughter, Peter Walter, Scott Wandel, Linda Young, Christoph Bostedt, Philip H Bucksbaum, Antonio Picon, Agostino Marinelli, James P Cryan, ​‘Electronic population transfer via impulsive stimulated x-ray Raman scattering with attosecond soft-x-ray pulses,” Physical Review Letters 125, 073203 (2020).
• Ludvig Kjellsson, K.D. Nanda, J.-E. Rubensson, G. Doumy, S.H. Southworth, P.J. Ho, A.M. March, A. Al Haddad, Y. Kumagai, M-F. Tu, R.D. Schaller, T. Debnath, M.S. Bin Mohd Yusof, C. Arnold, W.F. Schlotter, S. Moeller, G. Coslovich, J.D. Koralek, M.P. Minitti, Marta Lopez Vidal, M. Simon, R. Santra, Z.-H. Loh, Sonia Coriani, A.I. Krylov, L. Young, ​“Resonant inelastic x-ray scattering reveals hidden local transitions of the aqueous OH radiIcal,” Physical Review Letters 124, 236001 (2020).
• Z.-H. Loh, G. Doumy, C. Arnold, L. Kjellsson, S.H. Southworth, A. Al Haddad, Y. Kumagai, M.-F. Tu, P.J. Ho, A.M. March, R.D. Schaller, M.S. Bin Mohd Yusof, T. Debnath, M. Simon, R. Welsch, L. Inhester, K. Khalili, K. Nanda, A.I. Krylov, S. Moeller, G. Coslovich, J. Koralek, M.P. Minitti, W.F. Schlotter, J.-E. Rubensson, R. Santra, L. Young, ​“Observation of the fastest chemical processes in the radiolysis of water,” Science 367, 179-182 (2020). doi: 10.1126/science.aaz4740
• Dimitris Koulentianos, Adam E A Fouda, Stephen H Southworth, John D Bozek, Jochen Kupper, Robin Santra, NV Kryzhevoi, Lorenz S Cederbaum, Christoph Bostedt, Mark Messerschmidt, Nora Berrah, Li Fang, Brendan Murphy, Timur Osipov, James Patrick Cryan, J Glownia, Shambhu Ghimire, Phay J Ho, B Krassig, Dipanwita Ray, Yuelin Li, EP Kanter, Linda Young, Gilles Doumy, ​“High intensity x-ray interaction with a model bio-molecule system: double-core-hole states and fragmentation of formamide,” J. Phys. B: At. Mol. Opt. Phys. 53, 244005 (2020).
• A.E.A. Fouda, P.J. Ho, R.W. Dunford, E.P. Kanter, B. Krassig, L. Young, E.R. Peterson, E.C. Landahl, L. Pan, D.R. Beck, S.H. Southworth, ​“Resonant x-ray absorption of strong-field-ionized CF3Br,” J. Phys. B: At. Mol. Opt. Phys. 53, 244009 (2020).
• Phay J. Ho, Benedikt J. Daurer, Max F. Hantke, Johan Bielecki, Andre Al Haddad,Max Bucher,Gilles Doumy, Ken Ferguson, Leonie Fluckiger, Tais Gorkhover, Bianca Iwan, Christopher Knight, Stefan Moeller, Timur Osipov, Dipanwita Ray, Stephen H. Southworth, Martin Svenda, Nicusor Timneanu, Anatoli Ulmer, Peter Walter, Janos Hajdu, Linda Young, Filipe R.N.C. Maia and Christoph Bostedt, ​“The role of transient resonances for ultra-fast imaging of single sucrose nanoclusters,” Nature Communications 11, 167 (2020).
• Phay J. Ho, and Chris Knight, ​“Large-scale atomistic calculations of cluster in intense x-ray pulses,” J. Phys.B: At. Mol. Opt. Phys.50, 104003 (2017).
• Phay J. Ho, Chris Knight, Miklos Tegze, Gyula Faigel, C. Bostedt, and L. Young, ​“Atomistic 3D coherent X-ray imaging of non-biological systems,” Phys. Rev. A 94, 063823 (2016).