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 reactive scattering and photodissociation

Spectroscopy and dynamics in helium droplets

Attosecond spectroscopy

Spectroscopy and dynamics in liquid microjets

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Slow Photoelectron Velocity-Map Imaging (SEVI)

Synopsis:

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.

Molecules studied recently:

Vinylidene (H2CC)

Metal oxide clusters: Ti2O4, Zr2O4, VO2, Fe3O, Co3O, FeO

Polycyclic aromatic hydrocarbons: naphthyl (C10H8), indenyl (C9H7), fluorenyl (C13H9)

Interstellar molecules: CH2CN, C5, S3

Transition state spectroscopy: F + CH4, H2

Project members:

Jessalyn DeVine

Mark Babin

Recent publications:

♦ "Low-lying vibronic level structure of the ground state of the methoxy radical: Slow electron velocity-map imaging (SEVI) spectra and Koppel-Domcke-Cederbaum (KDC) vibronic Hamiltonian calculations" M. L. Weichman, L. Cheng, J. B. Kim, J. F. Stanton, D. M. Neumark, J. Chem. Phys. 146, 224309 (2017). pdf

♦ "Slow photoelectron velocity-map imaging of cold tert-butyl peroxide" J. A. DeVine, M. L. Weichman, M. C. Babin, Daniel M. Neumark, J. Chem. Phys. 147, 013915 (2017). pdf

♦ "Non-Adiabatic Effects on Excited States of Vinylidene Observed with Slow Photoelectron Velocity-Map Imaging" J. A. DeVine, M. L. Weichman, X. Zhou, J. Ma, B. Jiang, H. Guo, D. M. Neumark, J. Am. Chem. Soc. 138, 16417 (2016). pdf

♦ "High-resolution photoelectron imaging of cryogenically cooled α- and β-furanyl anions" J. A. DeVine, M. L. Weichman, S. J. Lyle, D. M. Neumark, J. Mol. Spec. 332, 16 (2017). pdf

♦ "High-resolution photoelectron imaging spectroscopy of cryogenically cooled Fe4O- and Fe5O-" M. L. Weichman, J. A. DeVine, D. M. Neumark, J. Chem. Phys. 145, 054302 (2016). pdf