# Faculty and Staff

### Current Position

http://tccl.chem.umt.edu/chem_573_0.pdf

### Personal Summary

Xi Chu joined the UM chemistry faculty in 2005 as an assistant professor. She did her graduate study in the theoretical chemistry group of the University of Kansas and received her Ph.D. degree in 2001. Xi carried on postdoctoral research at the institute of theoretical atomic, molecular, and optical physics (ITAMP) in Harvard Smithsonian Center for Astrophysics. Xi Chu is a theoretical and computational quantum chemist.

### Research Interests

Our research is directed towards understanding the electronic structure, geometry, and dynamics of molecules of technological or fundamental interests. Ab initio or semi-empirical quantum mechanics and numerical approaches are developed to obtain desired results.

**Ultra-fast intense laser fields** In intense laser fields, many-electron systems produce striking nonlinear phenomena that can be employed for new technologies to detect and to shape electronic structures, and to control electronic or nuclear motions. Nonlinear responses also play an increasing role in creating new laser sources, controlling other fields, and performing logical operations.

It takes a detailed knowledge of the electronic structure of the ground state, highly excited states, the continuum, and the electron dynamics to fully understand strong field processes. Time-dependent density functional theory (TDDFT) is a reformulation of time-dependent quantum mechanics, so that computation is feasible for complex systems. Using TDDFT we look at the following processes:

Molecular orientation dependent strong field ionization and high order harmonic spectra.

Photochemical processes in electronically excited states.

Modifying potential energy surfaces with lasers to control the approach and recoil of molecules in collisions.

**Dispersion interactions** We determine long-range interactions between complex atomic pairs, which provide an assessment of the likelihood that specific atoms can be cooled in magnetic traps. Trapped and cooled atoms may form Bose-Einstein condensates, new sources of quantum systems, in which atom waves are manipulated much like light waves.

We are also interested in the non-bonding interactions between molecules and nano-structures, which may be employed in the application of molecular carrier or molecular transportation.

**Macroscopic quantum devices **Superconducting electronics have a wide range of commercial and medical applications. The radio-frequency superconducting quantum interference device (SQUID) and the Josephson tunnel junction (JTJ) can be used as quantum bits (qubits). This design offers devices with little dissipation, ultrasensitive magnetometers and electrometers for state readout, large-scale-integration, and a family of classical electronics that could be used for quantum qubit control. We model the quantum structure and dynamics of superconducting qubits and the time evolution of unstable two-level quantum systems, which provides theoretical insight on and numerical predictions of coherent temporal oscillations of excited state populations and phase decoherence time.

**TDDFT/MM approach for the study of photoreactions of macromolecules** Theoretical study of these reactions can assist the synthesis of photoactive materials and improve the selectivity of laser chemical reactions. The numerical simulation of these reactions is essential in interpreting experiments, predicting and visualizing pathways, and simulating extreme conditions.

### Selected Publications

Contributions of inner-valence molec orbitals and multiphoton resonances to high-order-harmonic generation of N 2 : A time-dependent density-functional-theory study, Xi Chu and Gerrit Groenenboom,* Phys. Rev. A * **93**, 013422 (2016).

Catalytic Mechanism of Mammalian Adenylyl Cyclase: A Computational Investigation , David K. Hahn, Jose R. Tusell, Stephen R. Sprang, and Xi Chu, * Biochemistry * **54**, 6252 (2015).

Cold magnetically trapped 2 D g sc atoms. I. Interaction potential, Tijs Carman, Xi Chu and Gerrit Groenenboom,* Phys. Rev. A * **90**, 052701 (2014).

Role of resonance-enhanced multiphoton excitation in high-harmonic generation of N2: A time-dependent density-functional-theory study, Xi Chu and Gerrit Groenenboom,* Phys. Rev. A * **87**, 013434 (2013).

Time-dependent density-functional-theory calculation of high-order-harmonic generation of H2, Xi Chu and Gerrit Groenenboom,* Phys. Rev. A * **85**, 053402 (2012).

Role of multiphoton excitation and two-electron effects in high harmonic generation of H2: A TDDFT calculation, Xi Chu and Patric J Memoli,* Chem. Phys. * **391**, 83 (2011).

Comparison of the strong-field ionization of N2 and F2: A time-dependent Comparison of the strong-field ionization of N2 and F2: A time-dependent density-functional-theory study, Xi Chu and Melissa McIntyre,* Phys. Rev. A * **83**, 013409 (2011).

Time-dependent density-functional-theory calculation of strong-field ionization rates of H2 Xi Chu, *Phys. Rev. A * **82**, 023407 (2010).

Molecular orientation dependent AC Stark effect and its impact on multiphoton processes , Xi Chu, *Phys. Rev. A ***78**, 043408 (2008).

Predicting Thermodynamic Properties with a Novel Semiempirical Topological Descriptor and Path Numbers Congyi Zhou, Xi Chu, and Changming Nie, * J. Phys. Chem. B * **111**, 10174 (2007).

Spectroscopic and Computational Studies of a Ru(II) Terpyridine Complex: The Importance of Weak Intermolecular Forces to Photophysical Properties , Claudio Garino, Roberto Gobetto, Carlo Nervi, Luca Salassa, Edward Rosenberg, J. B. Alexander Ross, Xi Chu, Kenneth I. Hardcastle, and Cristiana Sabatini, *Inorg. Chem. ***46**, 8752 (2007).

Dynamic polarizabilities of rare-earth-metal atoms and dispersion coefficients for their interaction with helium atoms X. Chu, A. Dalgarno, and G. C. Groenenboom,*Phys. Rev. A ***75**, 032723 (2007).

Electronic anisotropy between open shell atoms in first and second order perturbation theory G. C. Groenenboom, X. Chu, and R. V. Krems *J. Phys. Chem ***126**, 264306 (2007).

"Polarizabilities of Sc and Ti atoms and dispersion coefficients for their interaction with helium atoms" X. Chu, A. Dalgarno, and G. C. Groenenboom, *Phys. Rev. A***72**, 032703 (2005).

**Chu X**, **Dalgarno A**

Polarizabilities of ^3P atoms and van der Waals coefficients for their interaction with helium atoms

ADVANCES IN ATOMIC, MOLECULAR AND OPTICAL PHYSICS, VOL. 51: No. 83-89 2005

### Publications

For a complete list of publications, please go to

### Specialized Research Interests

Ab initio or semi-empirical quantum mechanics applied to the transition states stabilized by enzymes and the behavior of many-electron systems in ultra-fast intense laser fields.