On the photoabsorption by permanganate ions in vacuo and the role of a single water molecule. New experimental benchmarks for electronic structure theory.
We report electronic spectra of mass-selected MnO4(-) and MnO4(-)⋅H2O using electronic photodissociation spectroscopy. Bare MnO4(-) fragments by formation of MnO3(-) and MnO2(-), while the hydrated complex predominantly decays by loss of the water molecule. The band in the visible spectral region shows a well-resolved vibrational progression consistent with the excitation of a Mn-O stretching mode. The presence of a single water molecule does not significantly perturb the spectrum of MnO4(-). Comparison with the UV/Vis absorption spectrum of permanganate in aqueous solution shows that complete hydration causes a small blueshift, while theoretical models including a dielectric medium have predicted a redshift. The experimental data can be used as benchmarks for electronic structure theory methods, which usually predict electronic spectra in the absence of a chemical environment.
Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark.
Jørgen
J
Houmøller
Sydney H
SH
Kaufman
Kristian
K
Støchkel
Lokesh C
LC
Tribedi
Steen
S
Brøndsted Nielsen
J Mathias
JM
Weber