Spectroscopic signatures of HHe<sub>2</sub><sup>+</sup> and HHe<sub>3</sub><sup>+</sup>
Matthias Töpfer, Anders W. Jensen, Keigo Nagamori, Hiroshi Kohguchi, Tamás Szidarovszky, Attila G. Császár, Stephan Śchlemmer, Oskar Asvany
Abstract
Using two different action spectroscopic techniques, a high-resolution quantum cascade laser operating around 1300 cm-1 and a cryogenic ion trap machine, the proton shuttle motion of the cations HHe2+ and HHe3+ has been probed at a nominal temperature of 4 K. For HHe3+, the loosely bound character of this complex allowed predissociation spectroscopy to be used, and the observed broad features point to a lifetime of a few ps in the vibrationally excited state. For He-H+-He, a fundamental linear molecule consisting of only three nuclei and four electrons, the method of laser-induced inhibition of complex growth (LIICG) enabled the measurement of three accurate rovibrational transitions, pinning down its molecular parameters for the first time.