skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: High-resolution photoelectron imaging spectroscopy of cryogenically cooled Fe{sub 4}O{sup −} and Fe{sub 5}O{sup −}

Abstract

We report high-resolution photodetachment spectra of the cryogenically cooled iron monoxide clusters Fe{sub 4}O{sup −} and Fe{sub 5}O{sup −} obtained with slow photoelectron velocity-map imaging (cryo-SEVI). Well-resolved vibrational progressions are observed in both sets of spectra, and transitions to low-lying excited states of both species are seen. In order to identify the structural isomers, electronic states, and vibrational modes that contribute to the cryo-SEVI spectra of these clusters, experimental results are compared with density functional theory calculations and Franck-Condon simulations. The main bands observed in the SEVI spectra are assigned to the {sup 15}A{sub 2}←{sup 16}B{sub 2} photodetachment transition of Fe{sub 4}O{sup −} and the {sup 17}A′←{sup 18}A″ photodetachment transition of Fe{sub 5}O{sup −}. We report electron affinities of 1.6980(3) eV for Fe{sub 4}O and 1.8616(3) eV for Fe{sub 5}O, although there is some uncertainty as to whether the {sup 15}A{sub 2} state is the true ground state of Fe{sub 4}O. The iron atoms have a distorted tetrahedral geometry in Fe{sub 4}O{sup 0/−} and a distorted trigonal-bipyramidal arrangement in Fe{sub 5}O{sup 0/−}. For both neutral and anionic species, the oxygen atom preferably binds in a μ{sub 2}-oxo configuration along the cluster edge. This finding is in contrast to prior predictionsmore » that Fe{sub 5}O{sup 0/−} exhibits a μ{sub 3} face-bound structure.« less

Authors:
;  [1];  [1];  [2]
  1. Department of Chemistry, University of California, Berkeley, California 94720 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
22678970
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 145; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DENSITY FUNCTIONAL METHOD; EXCITED STATES; EXPERIMENTAL DATA; GROUND STATES; IRON IONS; IRON OXIDES; PHOTOELECTRON SPECTROSCOPY; SPECTRA

Citation Formats

Weichman, Marissa L., DeVine, Jessalyn A., Neumark, Daniel M., E-mail: dneumark@berkeley.edu, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720. High-resolution photoelectron imaging spectroscopy of cryogenically cooled Fe{sub 4}O{sup −} and Fe{sub 5}O{sup −}. United States: N. p., 2016. Web. doi:10.1063/1.4960176.
Weichman, Marissa L., DeVine, Jessalyn A., Neumark, Daniel M., E-mail: dneumark@berkeley.edu, & Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720. High-resolution photoelectron imaging spectroscopy of cryogenically cooled Fe{sub 4}O{sup −} and Fe{sub 5}O{sup −}. United States. doi:10.1063/1.4960176.
Weichman, Marissa L., DeVine, Jessalyn A., Neumark, Daniel M., E-mail: dneumark@berkeley.edu, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720. Sun . "High-resolution photoelectron imaging spectroscopy of cryogenically cooled Fe{sub 4}O{sup −} and Fe{sub 5}O{sup −}". United States. doi:10.1063/1.4960176.
@article{osti_22678970,
title = {High-resolution photoelectron imaging spectroscopy of cryogenically cooled Fe{sub 4}O{sup −} and Fe{sub 5}O{sup −}},
author = {Weichman, Marissa L. and DeVine, Jessalyn A. and Neumark, Daniel M., E-mail: dneumark@berkeley.edu and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720},
abstractNote = {We report high-resolution photodetachment spectra of the cryogenically cooled iron monoxide clusters Fe{sub 4}O{sup −} and Fe{sub 5}O{sup −} obtained with slow photoelectron velocity-map imaging (cryo-SEVI). Well-resolved vibrational progressions are observed in both sets of spectra, and transitions to low-lying excited states of both species are seen. In order to identify the structural isomers, electronic states, and vibrational modes that contribute to the cryo-SEVI spectra of these clusters, experimental results are compared with density functional theory calculations and Franck-Condon simulations. The main bands observed in the SEVI spectra are assigned to the {sup 15}A{sub 2}←{sup 16}B{sub 2} photodetachment transition of Fe{sub 4}O{sup −} and the {sup 17}A′←{sup 18}A″ photodetachment transition of Fe{sub 5}O{sup −}. We report electron affinities of 1.6980(3) eV for Fe{sub 4}O and 1.8616(3) eV for Fe{sub 5}O, although there is some uncertainty as to whether the {sup 15}A{sub 2} state is the true ground state of Fe{sub 4}O. The iron atoms have a distorted tetrahedral geometry in Fe{sub 4}O{sup 0/−} and a distorted trigonal-bipyramidal arrangement in Fe{sub 5}O{sup 0/−}. For both neutral and anionic species, the oxygen atom preferably binds in a μ{sub 2}-oxo configuration along the cluster edge. This finding is in contrast to prior predictions that Fe{sub 5}O{sup 0/−} exhibits a μ{sub 3} face-bound structure.},
doi = {10.1063/1.4960176},
journal = {Journal of Chemical Physics},
number = 5,
volume = 145,
place = {United States},
year = {Sun Aug 07 00:00:00 EDT 2016},
month = {Sun Aug 07 00:00:00 EDT 2016}
}
  • Cited by 1
  • The electronic and vibrational structures of Au{sub 2}Al{sub 2}{sup −} and Au{sub 2}Al{sub 2} have been investigated using photoelectron spectroscopy (PES), high-resolution photoelectron imaging, and theoretical calculations. Photoelectron spectra taken at high photon energies with a magnetic-bottle apparatus reveal numerous detachment transitions and a large energy gap for the neutral Au{sub 2}Al{sub 2}. Vibrationally resolved PE spectra are obtained using high-resolution photoelectron imaging for the ground state detachment transition of Au{sub 2}Al{sub 2}{sup −} at various photon energies (670.55−843.03 nm). An accurate electron affinity of 1.4438(8) eV is obtained for the Au{sub 2}Al{sub 2} neutral cluster, as well as twomore » vibrational frequencies at 57 ± 8 and 305 ± 13 cm{sup −1}. Hot bands transitions yield two vibrational frequencies for Au{sub 2}Al{sub 2}{sup −} at 57 ± 10 and 144 ± 12 cm{sup −1}. The obtained vibrational and electronic structure information is compared with density functional calculations, unequivocally confirming that both Au{sub 2}Al{sub 2}{sup −} and Au{sub 2}Al{sub 2} possess C{sub 2v} tetrahedral structures.« less
  • We report high-resolution photoelectron spectra of the transition metal suboxide clusters Fe{sub 3}O{sup −} and Co{sub 3}O{sup −}{sub .} The combination of slow electron velocity-map imaging and cryogenic cooling yields vibrationally well-resolved spectra, from which we obtain precise values of 1.4408(3) and 1.3951(4) eV for the electron affinities of Fe{sub 3}O and Co{sub 3}O. Several vibrational frequencies of the neutral ground state Fe{sub 3}O and Co{sub 3}O clusters are assigned for the first time, and a low-lying excited state of Fe{sub 3}O is observed. The experimental results are compared with density functional electronic structure calculations and Franck-Condon spectral simulations, enablingmore » identification of the structural isomer and electronic states. As has been found in photoelectron spectra of other trimetal oxo species, Fe{sub 3}O{sup 0/−} and Co{sub 3}O{sup 0/−} are assigned to a μ{sub 2}-oxo isomer with planar C{sub 2v} symmetry. We identify the ground states of Fe{sub 3}O{sup –} and Co{sub 3}O{sup –} as {sup 12}A{sub 1} and {sup 9}B{sub 2} states, respectively. From these states we observe photodetachment to the {sup 11}B{sub 2} ground and {sup 13}A{sub 1} excited states of Fe{sub 3}O, as well as to the {sup 8}A{sub 1} ground state of Co{sub 3}O.« less
  • We have measured the pulsed field ionization photoelectron (PFI-PE) spectrum of O{sub 2} in the energy range of 24.53{endash}25.0 eV at a PFI-PE resolution of 11thinspcm{sup {minus}1} (full width at half maximum, FWHM). The PFI-PE bands for O{sub 2}{sup +}(cthinsp{sup 4}{Sigma}{sub u}{sup {minus}}, v{sup +}=0 and 1) obtained at O{sub 2} rotational temperatures of 35 and 298 K have been simulated using the Buckingham{endash}Orr{endash}Sichel model. Only the {Delta}N={minus}3, {minus}1, +1, and +3 (or N, P, R, and T) rotational branches are observed, indicating that the outgoing electron continuum channels with angular momenta l=0, 2, and 4 dominate in the thresholdmore » ionization transitions O{sub 2}{sup +}(cthinsp{sup 4}{Sigma}{sub u}{sup {minus}}, v{sup +}=0 to 1, N{sup +}){l_arrow}O{sub 2}(Xthinsp{sup 3}{Sigma}{sub g}{sup {minus}}, v{sup {double_prime}}=0, N{sup {double_prime}}). The simulation yields natural rotational linewidths of 19.6{plus_minus}2.0 and 77{plus_minus}8thinspcm{sup {minus}1} (FWHM) for the respective v{sup +}=0 and 1 PFI-PE bands of the O{sub 2}{sup +}(cthinsp{sup 4}{Sigma}{sub u}{sup {minus}}) state. These linewidths make possible the determination of the predissociation lifetimes for the v{sup +}=0 and 1 levels of O{sub 2}{sup +}(cthinsp{sup 4}{Sigma}{sub u}{sup {minus}}) to be (2.7{plus_minus}0.3){times}10{sup {minus}13} and (6.9{plus_minus}0.7){times}10{sup {minus}14}thinsps, respectively. This experiment also provides accurate ionization energies of 24.5622{sub 7}{plus_minus}0.0005 and 24.7544{sub 5}{plus_minus}0.0005thinspeV for transitions to O{sub 2}{sup +}(cthinsp{sup 4}{Sigma}{sub u}{sup {minus}}, v{sup +}=0, N{sup +}=0) and O{sub 2}{sup +}(cthinsp{sup 4}{Sigma}{sub u}{sup {minus}}, v{sup +}=1, N{sup +}=0) from O{sub 2}(Xthinsp{sup 3}{Sigma}{sub g}{sup {minus}}, v{sup {double_prime}}, N{sup {double_prime}}=1), respectively. The rotational constants of 1.58{plus_minus}0.02 and 1.54{plus_minus}0.04thinspcm{sup {minus}1} obtained here for the O{sub 2}{sup +}(cthinsp{sup 4}{Sigma}{sub u}{sup {minus}}, v{sup +}=0) and O{sub 2}{sup +}(cthinsp{sup 4}{Sigma}{sub u}{sup {minus}}, v{sup +}=1) states allow the calculation of their corresponding equilibrium bond distances to be 1.155{plus_minus}0.011 and 1.170{plus_minus}0.015thinsp{Angstrom}. The (nominal) effective lifetimes for high-n Rydberg states converging to the O{sub 2}{sup +}(cthinsp{sup 4}{Sigma}{sub u}{sup {minus}}, v{sup +}=0 and 1) states are measured to be {approx}0.33thinsp{mu}s, which are significantly shorter than the values of {approx}1.9thinsp{mu}s measured for the O{sub 2}{sup +}(bthinsp{sup 4}{Sigma}{sub g}{sup {minus}}, v{sup +}=0{endash}5) states. The shorter (nominal) effective lifetimes for high-n Rydberg states converging to O{sub 2}{sup +}(cthinsp{sup 4}{Sigma}{sub g}{sup {minus}}, v{sup +}=0 and 1) observed are attributed to the higher kinetic energy releases (or velocities) of O{sup +} fragments resulting from predissociation of the O{sub 2}{sup +} ion cores. {copyright} {ital 1998 American Institute of Physics.}« less
  • Photodetachment cross sections are measured across the detachment threshold of Au{sub 2}{sup −} between 1.90 and 2.02 eV using a tunable laser. In addition to obtaining a more accurate electron affinity for Au{sub 2} (1.9393 ± 0.0003 eV), we observe eight resonances above the detachment threshold, corresponding to excitations from the vibrational levels of the Au{sub 2}{sup −} ground state (X {sup 2}Σ{sub u}{sup +}) to those of a metastable excited state of Au{sub 2}{sup −} (or Feshbach resonances) at an excitation energy of 1.9717 ± 0.0003 eV and a vibrational frequency of 129.1 ± 1.5 cm{sup −1}. High-resolution photoelectronmore » spectra of Au{sub 2}{sup −} are obtained using photoelectron imaging to follow the autodetachment processes by tuning the detachment laser to all the eight Feshbach resonances. We observe significant non-Franck-Condon behaviors in the resonant photoelectron spectra due to autodetachment from a given vibrational level of the Feshbach state to selective vibrational levels of the neutral final state. Using the spectroscopic data for the ground states of Au{sub 2}{sup −} (X {sup 2}Σ{sub u}{sup +}) and Au{sub 2} (X {sup 1}Σ{sub g}{sup +}), we estimate an equilibrium bond distance of 2.53 ± 0.02 Å for the Feshbach state of Au{sub 2}{sup −} by simulating the Franck-Condon factors for the resonant excitation and autodetachment processes.« less