%0 Journal Article
%A Hansen, Christopher
S.
%A Kirk, Benjamin B.
%A Blanksby, Stephen J.
%A Trevitt, Adam J.
%D 2013
%T Ultraviolet
Photodissociation of the N‑Methylpyridinium
Ion: Action Spectroscopy and Product Characterization
%U https://acs.figshare.com/articles/journal_contribution/Ultraviolet_Photodissociation_of_the_i_N_i_Methylpyridinium_Ion_Action_Spectroscopy_and_Product_Characterization/2363083
%R 10.1021/jp4075515.s001
%2 https://acs.figshare.com/ndownloader/files/4002523
%K Action Spectroscopy
%K S 1 state
%K 36 000
%K C 5H
%K C 5D
%K methane coproduct
%K laser photodissociation mass spectrometry
%K C 5H C 5H
%K isotopologue
%K 43 000
%K CASSCF
%K photon wavenumber
%K quantum chemical calculations
%K cm
%K Ultraviolet Photodissociation
%K ground state surface
%K vibronic detail
%K Product CharacterizationThe
%K room temperature
%X The ultraviolet photodissociation
of gas-phase N-methylpyridinium ions is studied at
room temperature using laser
photodissociation mass spectrometry and structurally diagnostic ion–molecule
reaction kinetics. The C5H5N–CH3+ (m/z 94), C5H5N-CD3+ (m/z 97), and C5D5N–CH3+(m/z 99) isotopologues
are investigated, and it is shown that the N-methylpyridinium
ion photodissociates by the loss of methane in the 36 000 –
43 000 cm–1 (280 – 230 nm) region.
The dissociation likely occurs on the ground state surface following
internal conversion from the S1 state. For each isotopologue,
by monitoring the photofragmentation yield as a function of photon
wavenumber, a broad vibronically featured band is recorded with origin
(0–0) transitions assigned at 38 130, 38 140 and 38 320 cm–1 for C5H5N–CH3+ C5H5N-CD3+ and C5D5N–CH3+, respectively.
With the aid of quantum chemical calculations (CASSCF(6,6)/aug-cc-pVDZ),
most of the observed vibronic detail is assigned to two in-plane ring
deformation modes. Finally, using ion–molecule reactions,
the methane coproduct at m/z 78
is confirmed as a 2-pyridinylium ion.
%I ACS Publications