TY - JOUR
T1 - Photoelectron imaging of NCCCN-
T2 - The triplet ground state and the singlet-triplet splitting of dicyanocarbene
AU - Goebbert, Daniel J.
AU - Pichugin, Kostyantyn
AU - Khuseynov, Dmitry
AU - Wenthold, Paul G.
AU - Sanov, Andrei
N1 - Funding Information:
This work was supported by the U.S. National Science Foundation under Grant No. CHE-0713880 (A.S.) and Grant Nos. CHE-0454874 and CHE-0808964 (P.W.). Calculations were carried out using the resources from the Center for Computational Studies of Open-Shell and Electronically Excited Species ( http://iopenshell.usc.edu ), directed by Professor Anna Krylov. We thank Professor Lyudmila Slipchenko for assistance with the electronic structure calculations and Dr. David Hrovat and Professor Weston T. Borden for providing the results of their CASPT2 calculations.
PY - 2010/6/14
Y1 - 2010/6/14
N2 - The photoelectron spectra of NCCCN- have been measured at 355 and 266 nm by means of photoelectron imaging. The spectra show two distinct features, corresponding to the ground and first excited states of dycianocarbene. With support from theoretical calculations using the spin-flip coupled-cluster methods, the ground electronic state of HCCCN is assigned as a triplet state, while the first excited state is a closed-shell singlet. The photoelectron band corresponding to the triplet is broad and congested, indicating a large geometry change between the anion and neutral. A single sharp feature of the singlet band suggests that the geometry of the excited neutral is similar to that of the anion. In agreement with these observations, theoretical calculations show that the neutral triplet state is either linear or quasilinear (X̃ 3B1 or 3∑-g), while the closed-shell singlet (ã 1A1) geometry is strongly bent, similar to the anion structure. The adiabatic electron binding energy of the closed-shell singlet is measured to be 3.72±0.02 eV. The best estimate of the origin of the triplet band gives an experimental upper bound of the adiabatic electron affinity of NCCCN, EA≤3.25±0.05 eV, while the Franck-Condon modeling yields an estimate of EA (NCCCN) =3.20±0.05 eV. From these results, the singlet-triplet splitting is estimated to be Δ EST (X̃3B1/3∑ -Bg-ã 1A1) =0.52±0.05 eV (12.0±1.2 kcal/mol).
AB - The photoelectron spectra of NCCCN- have been measured at 355 and 266 nm by means of photoelectron imaging. The spectra show two distinct features, corresponding to the ground and first excited states of dycianocarbene. With support from theoretical calculations using the spin-flip coupled-cluster methods, the ground electronic state of HCCCN is assigned as a triplet state, while the first excited state is a closed-shell singlet. The photoelectron band corresponding to the triplet is broad and congested, indicating a large geometry change between the anion and neutral. A single sharp feature of the singlet band suggests that the geometry of the excited neutral is similar to that of the anion. In agreement with these observations, theoretical calculations show that the neutral triplet state is either linear or quasilinear (X̃ 3B1 or 3∑-g), while the closed-shell singlet (ã 1A1) geometry is strongly bent, similar to the anion structure. The adiabatic electron binding energy of the closed-shell singlet is measured to be 3.72±0.02 eV. The best estimate of the origin of the triplet band gives an experimental upper bound of the adiabatic electron affinity of NCCCN, EA≤3.25±0.05 eV, while the Franck-Condon modeling yields an estimate of EA (NCCCN) =3.20±0.05 eV. From these results, the singlet-triplet splitting is estimated to be Δ EST (X̃3B1/3∑ -Bg-ã 1A1) =0.52±0.05 eV (12.0±1.2 kcal/mol).
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U2 - 10.1063/1.3436717
DO - 10.1063/1.3436717
M3 - Article
C2 - 20550391
AN - SCOPUS:77953596019
SN - 0021-9606
VL - 132
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 22
M1 - 224301
ER -