The Neumark Group


Department of Chemistry, University of California Berkeley
and Chemical Science Division, Lawrence Berkeley National Laboratory

Slow photoelectron velocity-map imaging spectroscopy

Fast beam translational spectroscopy

Femtosecond time-resolved photoelectron imaging

Flat liquid jet molecular beam scattering

Spectroscopy and dynamics in helium droplets

Attosecond spectroscopy

Spectroscopy and dynamics in liquid microjets

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Slow Photoelectron Velocity-Map Imaging (SEVI)


SEVI is a variant of conventional anion photoelectron spectroscopy which combines a velocity-map imaging (VMI) detection scheme and tunable photodetachment energy. Anions are cryogenically cooled to temperatures as low as 5 K in a radiofrequency ion trap, then mass-selected and photodetached at energies 0.01-0.5 eV above threshold. The resulting photoelectrons are collected using relatively low extraction voltages, with the goal of selectively detecting slow electrons with high efficiency and enlarging their image on the detector. At each wavelength, one obtains a high resolution (up to 1 cm-1) photoelectron spectrum over a limited range of electron kinetic energy as well as the photoelectron angular distributions.

The SEVI spectra give the electronic and vibrational energy levels of the neutral molecule in high-resolution. In combination with ab initio electronic structure calculations and Franck-Condon simulations, the SEVI experiment yields information on the geometry, vibrational frequencies and electronic structure of both the anion and neutral states.

A recent review can be found here.

Molecules studied:

Vinylidene (H2CC)

Metal oxide clusters: FenO (n=1-5); VO2; SmO

Combustion-relevant radicals: methoxy (CH3O), t-butyl peroxy (C4H9OO), furanyl (C4H3O)

Transition state spectroscopy: F + CH3OH, CH4, H2

Project members:

Martin DeWitt

Jascha Lau

Korina Vlahos

Recent publications:

♦ "High-resolution photoelectron spectroscopy of vibrationally excited vinoxide anions" J. A. Lau, M. DeWitt, M. A. Boyer, M. C. Babin, T. Solomis, M. Grellmann, K. R. Asmis, A. B. McCoy, D. M. Neumark, J. Phys. Chem. A, 127, 3133–3147 (2023). pdf

♦ "Observation of resonances in the transition state region of the F + NH3 reaction using anion photoelectron spectroscopy" M. C. Babin, M. DeWitt, J. A. Lau, M. L. Weichman, J. B. Kim, H. Song, H. Guo, D. M. Neumark, Nat. Chem. (2022). pdf

♦ "High Resolution Photoelectron Spectroscopy of the Acetyl Anion" M. DeWitt, M. C. Babin, J. A. Lau, T. Solomis, D. M. Neumark, J. Phys. Chem. A 126, 7962–7970 (2021). pdf

♦ "Electronic structure of NdO via slow photoelectron velocity-map imaging spectroscopy of NdO-" M. C. Babin, M. DeWitt, J. A. DeVine, D. C. McDonald, S. G. Ard, N. S. Shuman, A. A. Viggiano, L. Cheng, D. M. Neumark, J. Chem. Phys. 155, 114301 (2021). pdf

♦ "High-Resolution Photoelectron Spectroscopy of Vibrationally Excited OH-" M. DeWitt, M. C. Babin, D. M. Neumark, J. Phys Chem. A 125, 7260 (2021). pdf