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
Molecular beam photodissociation dynamics
Spectroscopy and dynamics in helium droplets
Spectroscopy and dynamics in liquid microjets
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 recently:
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
♦ "High-resolution photoelectron spectroscopy of TiO3H2-: Probing the TiO2- + H2O dissociative adduct" J. A. DeVine, A. A. Taka, M. C. Babin, M. L. Weichman, H. P. Hratchian, D. M. Neumark, J. Chem. Phys. 148, 222810 (2018). pdf
♦ "Autodetachment from vibrationally excited vinylidene anions" J. A. DeVine, M. L. Weichman, C. Xie, M. C. Babin, M. A. Johnson, J. Ma, H. Guo, D. M. Neumark, J. Phys. Chem. Lett. 9, 1058 (2018). pdf
♦ "Electronic structure of SmO and SmO- via slow photoelectron velocity-map imaging spectroscopy and spin-orbit CASPT2 calculations" M. L. Weichman, B. Vlaisavljevich, J. A. DeVine, N. S. Shuman, S. G. Ard, T. Shiozaki, D. M. Neumark, A. A. Viggiano, J. Chem. Phys. 147, 234311 (2017). pdf
♦ "Encoding of vinylidene isomerization in its anion photoelectron spectrum" J. A. DeVine, M. L. Weichman, B. Laws, J. Chang, M. C. Babin, G. Balerdi, C. Xie, C. L. Malbon, W. C. Lineberger, D. R. Yarkony, R. W. Field, S. T. Gibson, J. Ma, H. Guo, D. M. Neumark, Science 358, 336 (2017). pdf