Abstract
We have measured depletion spectra of the heteronuclear (85Rb87Rb+) dimer cation complexed with up to 10 He atoms. Two absorption bands are observed between 920 and 250 nm. The transition into the repulsive 12Σu+ state of HeRb2+ gives rise to a broad feature at 790 nm (12,650 cm−1); it exhibits a blueshift of 98 cm−1 per added He atom. The transition into the bound 12Πu state of HeRb2+ reveals vibrational structure with a band head at ≤ 15,522 cm−1, a harmonic constant of 26 cm−1, and a spin–orbit splitting of ≤ 183 cm−1. The band experiences an average redshift of − 38 cm−1 per added He atom. Ab initio calculations rationalize the shape of the spectra and spectral shifts with respect to the number of helium atoms attached. For a higher number of solvating helium atoms, symmetric solvation on both ends of the Rb2+ ion is predicted.
Highlights
Helium nanodroplets have been used as nanocryostats to isolate atoms or molecules at a temperature of 0.4 K, or to form new weakly bound aggregates [1,2,3]
Alkali metal atoms reside on the surface of He droplets due to the short-range Pauli repulsion between their s valence electrons and surrounding helium atoms counteracting the Published as part of the special collection of articles “Festschrift in honor of Fernand Spiegelmann”
The ion beam was guided into the extraction region of a high-resolution time-of-flight mass spectrometer (TOFMS) where it was merged with a laser beam from a tunable light source (EKSPLA NT242, line width 5 cm−1, pulse duration 3–6 ns, repetition rate 1 kHz)
Summary
Helium nanodroplets have been used as nanocryostats to isolate atoms or molecules at a temperature of 0.4 K, or to form new weakly bound aggregates [1,2,3]. They offer a unique quantum solvent for studying small and large dopant clusters, neutral or ionic, which can in turn be investigated by electronic or infrared spectroscopy [4]. Alkali metal atoms reside on the surface of He droplets due to the short-range Pauli repulsion between their s valence electrons and surrounding helium atoms counteracting the Published as part of the special collection of articles “Festschrift in honor of Fernand Spiegelmann”
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