Ph. D. University of Arizona (2008)
President’s Postdoctoral Fellow, UC Santa Barbara (2008-2010)
Postdoctoral Research Associate, Pacific Northwest National Lab (2010-2013)
Ultrafast spectroscopy, interfacial processes, nonlinear microscopy, materials chemistry
Our research program focuses on the molecular-level elucidation of dynamic processes and structural characteristics underlying functional interfaces through direct spectral measurements of chemical bonds and molecular interactions at the complex surfaces of nanostructures and porous materials. Our interests include the synthesis of novel materials and the use of nonlinear laser spectroscopy and microscopy to unravel key processes in condensed-phase interfaces as they relate to the discovery of better ways of converting and storing energy as well as to the development of low-cost energy-efficient devices and more powerful and selective chemical sensors.
We integrate recent discoveries in materials and surface science with interface-selective ultrafast nonlinear optical techniques in order to gain detailed quantitative knowledge of the dynamic couplings between the surface electronic states and the molecular degrees of freedom in lower-dimensional and nano-scale environments. We are developing novel ways to provide in-situ measurements of the interfacial properties of organic and organic/inorganic composites by characterizing the surface electronic states, interfacial chemical identity, molecular orientation, binding, and electrochemical environment as they ultimately determine the device efficiency and performance.
Our studies also examine how the energy of an absorbed photon is transferred within different chemical groups of a surface molecule, among neighboring molecules, or to the interface where it can give raise to mobile carriers. Of special interest to our program is the effect that lattice and molecular vibrations, point defects, and adsorbates have in the outcomes of surface chemical reactions and interfacial charge and energy transfer processes.
Selected Recent Publications:
- Lu, A. Karakoti, L. Velarde, W. Wang, P. Yang, S. Thevuthasan, and H. F. Wang. Dissociative Binding of Carboxylic Acid Ligand on Nanoceria Surface in Aqueous Solution: A Joint In-Situ Spectroscopic Characterization and First-Principles Study. J. Phys. Chem. C 2013, 117, 24329.
- Velarde and H. F. Wang. Unified treatment and measurement of the spectral resolution and temporal effects in frequency-resolved sum-frequency generation vibrational spectroscopy (SFG-VS). Phys. Chem. Chem. Phys. 2013, 15, 19970-19984.
- Velarde and H. F. Wang. Unique determination of the –CN group tilt angle in Langmuir monolayers using sum-frequency polarization null angle and phase. Chem. Phys. Lett. 2013, 585, 42-48.
- Velarde and H. F. Wang. Capturing inhomogeneous broadening of the –CN stretch vibration in a Langmuir monolayer with high-resolution spectra and ultrafast vibrational dynamics in sum-frequency generation vibrational spectroscopy (SFG-VS). J. Chem. Phys. 2013, 139, 084204.
- Velarde, X. Y. Zhang, Z. Lu, A. Joly, Z.Wang, and H. F.Wang. Communication: Spectroscopic phase and lineshapes in high-resolution broadband sum frequency vibrational spectroscopy: Resolving interfacial inhomogeneities of identical molecular groups. J. Chem. Phys. 2011, 135, 241102.
- LaRue, T. Schäfer, D. Matsiev, L. Velarde, H. Nahler, D. J. Auerbach, and A. M. Wodtke. Vibrationally promoted electron emission at a metal surface: electron kinetic energy distributions. Phys. Chem. Chem. Phys. 2011, 13, 97-99.
- Velarde, D. Engelhart, D. Matsiev, J. LaRue, J. D. Auerbach, and A. M. Wodtke. Generation of tunable narrow bandwidth nanosecond pulses in the deep ultraviolet for efficient optical pumping and high resolution spectroscopy. Rev. Sci. Instr. 2010, 81, 063106.
- J. Goebbert, L. Velarde, D. Khuseynov, and A. Sanov. The C-H Bond Dissociation Energy of Malononitrile. J. Phys. Chem. Lett. 2010, 1, 792-795.
- Ichino, S. M. Villano, A. J. Gianola, D. J. Goebbert, L. Velarde, A. Sanov, S. J. Blanksby, X. Zhou, W. T. Borden, and W. C. Lineberger. The Lowest Singlet and Triplet States of the Oxyallyl Diradical. Angew. Chem. Int. Ed. 2009, 48, 8509-8511.
- Velarde, T. Habteyes, E. Grumbling, K. Pichugin, and A. Sanov. Solvent resonance effect on the anisotropy of NO–(N2O)n cluster anion photodetachment. J. Chem. Phys. 2007, 127, 084302.