Marcin Gronowski

Computational Chemistry

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Posts Tagged ‘Emission spectrum’

Electronic absorption and phosphorescence of cyanodiacetylene

Electronic absorption and emission spectra have been investigated for cyanodiacetylene, HC5N, an astrophysically relevant molecule. The analysis of gas-phase absorption was assisted with the parallel rare gas matrix isolation experiments and with density functional theory (DFT) predictions concerning the excited electronic states. Mid-UV systems: B1Δ←X1Σ+  (origin at 282.5 nm) and B1Σ←X1Σ+ (306.8 nm) were observed. Vibronic assignments have been facilitated by the discovery of the visible phosphorescence a3Σ+←X1Σ+ in solid Ar, Kr, and Xe. Phosphorescence excitation spectra, as well as UV absorption measurements in rare gas matrices, revealed the enhancement of A←X transitions. The vibronic structure of dispersed phosphorescence spectra supplied new data concerning the ground state bending fundamentals of matrix-isolated HC5N. The experimental singlet-triplet splitting, 2.92 eV in Ar, closely matches the value of 3.0 eV predicted by DFT.

Full text: J. Chem. Phys. 133 (2010) 074310

The C3N− anion: First detection of its electronic luminescence in rare gas solids

The 193 nm laser irradiation of cyanoacetylene HCCCN that was isolated in rare gas solids led to a long-lived luminescence origin at 3.58 eV, which was assigned to the a 3Σ+-X 1Σ+ system of cyanoacetylide CCCN−. The identification, which involved 15N and 2H isotopic substitution studies, is based on vibronic spacings in the phosphorescence spectrum compared to previous infrared absorption measurements and to theoretical results regarding CCCN− vibrational frequencies, as well as on a BD(T)/cc-pVTZ prediction for the singlet-triplet energy gap in this anion 3.61 eV. The same emission was also generated from Kr/HC3N mixtures subjected to a glow electric discharge immediately before the solidification cold-window-radial-discharge technique.
Full text: J. Chem. Phys. 128 (2008) 164304