Justin Jankunas Doctoral Dissertation Award in Chemical Physics Talk: Slow photoelectron velocity-map imaging (SEVI) spectroscopy of cryo-cooled anions
COFFEE_KLATCH · Invited
Abstract
Slow photoelectron velocity-map imaging spectroscopy of cryogenically-cooled anions (cryo-SEVI) is a powerful technique for elucidating the vibrational and electronic structure of exotic neutral species. SEVI is a high-resolution variant of anion photoelectron imaging that yields spectra with energy resolution as high as 1 cm−1. The preparation of cold anions eliminates hot bands and narrows rotational envelopes, enabling the acquisition of well-resolved photoelectron spectra for complex and spectroscopically challenging species.1,2
Recently, cryo-SEVI has been applied as a spectroscopic probe of transition state dynamics on neutral reactive surfaces, through photodetachment of a bound anion similar in geometry to the desired transition state. In the benchmark F + H2 reaction, we probe the transition state region through detachment of FH2− and directly observe new reactive resonances. Comparison to new theory allows for the assignment of resonances associated with quasi-bound states of the transition state and products.3 We also report spectra of the F + CH3OH hydrogen abstraction reaction through photodetachment of the CH3OHF− van der Waals clusters. We gain insight into the energetics and vibrational structure of transient complexes along the reaction coordinate of this complex polyatomic system.4
Finally, we report a new cryo-SEVI study of vinylidene (H2CC), a high energy isomer of acetylene, which is accessed directly through detachment of H2CC−. We find spectroscopic evidence that the isomerization of vinylidene to acetylene is highly state-specific, with excitation of the ν6 in-plane rocking mode resulting in appreciable tunneling-facilitated mixing with highly vibrationally excited states of acetylene.5
1JCP 137, 244201 (2012).
2PNAS 113, 1698 (2016).
3Science 349, 510 (2015).
4Nat. Chem. 9, 950 (2017).
5eScience 358, 336 (2017).
Recently, cryo-SEVI has been applied as a spectroscopic probe of transition state dynamics on neutral reactive surfaces, through photodetachment of a bound anion similar in geometry to the desired transition state. In the benchmark F + H2 reaction, we probe the transition state region through detachment of FH2− and directly observe new reactive resonances. Comparison to new theory allows for the assignment of resonances associated with quasi-bound states of the transition state and products.3 We also report spectra of the F + CH3OH hydrogen abstraction reaction through photodetachment of the CH3OHF− van der Waals clusters. We gain insight into the energetics and vibrational structure of transient complexes along the reaction coordinate of this complex polyatomic system.4
Finally, we report a new cryo-SEVI study of vinylidene (H2CC), a high energy isomer of acetylene, which is accessed directly through detachment of H2CC−. We find spectroscopic evidence that the isomerization of vinylidene to acetylene is highly state-specific, with excitation of the ν6 in-plane rocking mode resulting in appreciable tunneling-facilitated mixing with highly vibrationally excited states of acetylene.5
1JCP 137, 244201 (2012).
2PNAS 113, 1698 (2016).
3Science 349, 510 (2015).
4Nat. Chem. 9, 950 (2017).
5eScience 358, 336 (2017).
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Presenters
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Marissa Weichman
- University of Colorado Boulder