The ground state bending levels of 11BH2 have been studied experimentally using a combination of low-resolution emission spectroscopy and high-resolution stimulated emission pumping (SEP) measurements. The data encompass the energy range below, through, and above the calculated position of the barrier to linearity. For the bending levels (0,3,0) and above, the data show substantial K-reordering, with the K"a = 1 levels falling well below those with K"a = 0. A comparison of the high-resolution rotationally resolved SEP data to our own very high level ab initio calculations of the rovibronic energy levels shows agreement approaching near-spectroscopic accuracy (a few cm−1). The data reported in this work provide very stringent tests for future theoretical treatments of this prototypical seven-electron free radical.

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Published in The Journal of Chemical Physics, v. 147, issue 12, 124303, p. 1-13.

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The following article appeared in The Journal of Chemical Physics, v. 147, issue 12, 124303, p. 1-13 and may be found at https://doi.org/10.1063/1.4990760.

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This material is based upon work supported by the National Science Foundation under Grant No. CHE-1106338. R.T. acknowledges financial support from the University of Bologna.