Perturbation-facilitated detection of the first quintet-quintet band in C2.
The first high-spin transition in C2 (1 (5)Πu - 1 (5)Πg) is observed by perturbation-facilitated optical-optical double resonance spectroscopy. The experiment is performed by applying unfolded two-color resonant four-wave mixing. C2 radicals in the initial a (3)Πu, v = 5 state are produced by using a discharge source in a molecular beam environment. The final quintet state is excited via intermediate "gateway" states exhibiting both substantial triplet and quintet character due to a perturbation between the 1 (5)Πg, v = 0 and the d (3)Πg, v = 6 states. Fifty seven rotational transitions in the P, Q, and R branches of all spin sub-states are measured and yield accurate molecular constants of the newly found upper level 1 (5)Πu. In addition, satellite transitions (ΔJ ≠ ΔN) are observed and allow an accurate determination of the spin-orbit constant. The results are compared with high-level ab initio computations at the multi-reference configuration interaction level of theory. The high-lying quintet state is found to be predissociative and displays a shallow potential that accommodates three vibrational levels only.
Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
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Bornhauser
Laboratoire de Chimie Quantique, Institut de Chimie, Université de Strasbourg. 4, rue Blaise Pascal - CS90032 67081 STRASBOURG CEDEX, France.
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Marquardt
Laboratoire de Chimie Quantique, Institut de Chimie, Université de Strasbourg. 4, rue Blaise Pascal - CS90032 67081 STRASBOURG CEDEX, France.
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Gourlaouen
Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
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Knopp
Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
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Beck
Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
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Gerber
Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
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van Bokhoven
Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
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Radi