Education

PhD in Chemistry, UC Berkeley

[Aug. 2014 — Dec. 2019]

Thesis title: “Slow Electron Velocity-Map Imaging and Infrared Photodissociation of Cryogenically-Cooled Molecular Anions”
Thesis advisor: Prof. Daniel M. Neumark

BA in Chemistry, Rutgers University,

[Aug. 2009 — May 2014]

Graduated summa cum laude with a concentration in chemical physics and a double minor in physics and mathematics.

Postdoctoral Positions

  • Ethanol has been observed in various regions of space, in particular near young stars and protostars. Pure ethanol ices are not the norm; instead, it is embedded in ices made of simpler molecules such as CO and water. Laboratory studies which focus on the pure ice thus can only go so far. I am currently carrying out experiments aimed at understanding how the chemical picture changes with the icy environment by performing CRYOPAD experiments on carefully prepared ice mixtures and analyzing the changes that come with variation of the ice composition.

  • At present, we prepare ices by passing a gas mixture through a leak valve; as the gas freezes out onto our subtrate, we monitor the ice, and then close the leak valve. While this approach is experimentally facile, it comes with some drawbacks. Precisely controlling the thickness of the deposited ice relies on the experimentalist’s familiarity with the particular leak valve. Further, the lack of directionality in the gas flow means that we deposit on many places besides our substrate; this is an issue for temperature-programmed desorption measurements, which are crucial for assigning photoproducts in our experiments. I aim to improve upon these issues by instead using a pulsed molecular beam to deposit our ices.

Research

Leiden Observatory — Leiden, NL

Supervisors: Thanja Lamberts, Ewine van Dishoek

Supervisor: Alec Wodtke

Interstellar ice analogues, prepared in an ultra-high vacuum (UHV) chamber, are subjected to ultraviolet irradiation to induce chemical changes. The solid phase is monitored using infrared spectroscopy, while gas-phase products are detected with a quadrupole mass spectrometer.

[Feb. 2024 — present]

Georg-August University of Göttingen — Göttingen, DE

[Jan. 2023 — Jan. 2024]

Reactions on a heated metal surface in UHV conditions are initiated by molecular beam pulses; the resultant product molecules desorb, are ionized, and are detected using ion imaging. To observe species that do not thermally desorb — e.g. surface-bound reactive intermediates — an ultrafast laser is used to perform laser-induced desorption (LID).

  • Successfully implemented the LID-VRK capability into an existing setup, leading to the detection of atomic nitrogen formed during the catalytic oxidation of ammonia on a palladium surface.

  • Gained skills using python to control and monitor lab equipment.

Supervisor: Alec Wodtke

Max-Planck Institute for Multidisciplinary Sciences — Göttingen, DE

[Jan. 2020 — Jan. 2023]

CO crystals are prepared by pulsed molecular beam dosing on a sodium chloride substrate. Vibrational excitation is induced using a pulsed laser system comprising of an Nd:YAG-pumped tunable dye laser, the output of which undergoes difference frequency mixing with the Nd:YAG fundamental to generate tunable near-infrared light. Changes in the monolayer and overlayer structures are monitored using transmission FTIR spectroscopy.

  • While studying the vibrational relaxation dynamics of CO crystals adsorbed to a sodium chloride substrate, we accidentally discovered that excitation with our laser led to the formation of carbon-carbon bonds. The multi-photon vibrational energy pooling (VEP) process undergone by vibrationally excited CO crystals, in this case, provided access to a spin-forbidden pathway, providing an interesting example of vibrationally-driven chemistry. Read more.

  • When adsorbed to a sodium chloride substrate, carbon monoxide preferentially binds with the carbon atom facing towards the surface. The opposite configuration -- with the O-atom facing the surface -- is a metastable state, with a relatively low barrier to isomerization. These two isomers, due to the electrostatic impact of the surface on the CO bond, have different vibrational signatures, and evidence of the O-down isomer is seen in experiments where the VEP process of CO is induced. We find that the reconversion from O-down to C-down proceeds through tunneling, a somewhat surprising result given the relatively high masses of the particles involved. Read more.

Doctoral Research

UC Berkeley — Berkeley, CA, USA

Supervisor: Daniel Neumark

[Aug. 2014 — Dec. 2019]

My PhD thesis largely focused on high-resolution photoelectron spectroscopy on gas-phase anions, obtained using a state-of-the-art velocity-map imaging spectrometer that is optimized for the detection of slow electrons. A dye laser, tuned to be just above each transition of interest, enables acquisition of sub-meV-resolved vibronic spectra that reflect the physical properties of species, such as free radicals, which are notoriously evasive in common laboratory techniques. More details on this experiment can be found here.

  • The cryo-SEVI apparatus has several modes of ion generation that lend themselves to the study of different systems. For most species, electron impact ionization is used; this requires an appropriate precursor gas, and so is largely limited to organic species. To study metal oxide clusters, the molecular beam pulse is instead passed through a plasma generated by laser ablation of a metal target. I modified the laser ablation source to include a reactor chamber, allowing for the study of reactive complexes of metal oxide clusters.

  • A key aspect of the cryo-SEVI apparatus is the radiofrequency ion trap. Particularly in the case of plasma entrainment, the anions that we form are not always in the ground state; this vastly complicates the photoelectron spectra. By trapping the ions in an ion trap, filled with a cryogenically-cooled buffer gas, we cool the anions to as low as 5 K, giving orders-of-magnitude improvements in spectral resolution over prior spectra.

  • Crucial to the slow electron velocity-map imaging technique is the ability to generate laser pulses over a wide range of photon energies. The laser system is based around a dye laser pumped by either the second or third harmonic of an Nd:YAG laser. Nonlinear optical techniques may then be used to further extend the energy range that can be produced.

Fritz-Haber Institute — Berlin, DE

Supervisor: Knut Asmis

Undergraduate Research

Supervisor: Edward W. Castner, Jr.

Cornell University — Ithaca, NY, USA

Supervisor: Frank W. Wise

[Nov. 2018]

Thanks to an international collaboration, I spent a month working on an experiment based around the free electron laser (FEL) in Berlin. There, I used electrospray ionization to produce solvated cluster ions, which were mass-selected and cryogenically cooled through similar techniques to those used in Berkeley. The ions were tagged with a weakly-bound species, and exposed to the tunable infrared light generated by the FEL; when this light was resonant with a vibrational excitation in the anion, the tagging species is lost, providing a measurement of the IR absorption spectrum.

Rutgers University — New Brunswick, NJ, USA

[Sep. 2011 — Jun. 2014]

I was fortunate to have been given a great deal of independence in the lab as an undergraduate researcher. I gained experience using an ultrafast Ti:sapphire laser to perform fluorescence experiments aimed at studying the effects of solvents on electron transfer processes. Despite not having yet completed my studies, I was able to perform these experiments independently after some initial training, a degree of self-reliance I have maintained throughout my career.

[Summer 2011]

Following my second year of undergraduate studies, I was awarded a position in an REU (research experience for undergraduates) funded through the American National Science Foundation. In this position, I synthesized PbSe quantum dots and performed characterization of them using fluorescence spectroscopy and scanning electron microscopy.