Superfluidity Within a Small Helium-4 Cluster: The Microscopic Andronikashvili Experiment

Abstract

The infrared spectrum of single oxygen carbon sulfide (OCS) molecules was measured inside large superfluid pure helium-4 droplets and nonsuperfluid pure helium-3 droplets, both consisting of about 10(4) atoms. In the helium-4 droplets, sharp rotational lines were observed, whereas in helium-3 only a broad peak was found. This difference is interpreted as evidence that the narrow rotational lines, which imply free rotations, are a microscopic manifestation of superfluidity. Upon addition of 60 helium-4 atoms to the pure helium-3 droplets, the same sharp rotational lines were found; it appears that 60 is the minimum number needed for superfluidity.

Vibrational relaxation and dephasing of Rb2 attached to helium nanodroplets

“…7 (a)), the relative amplitudes only decrease in the case of the high-lying level beats (4,5) and (5,6), whereas the lower beats (3, 4) remain constant or even rise [(0, 1), (1,2), and (2, 3)] in amplitude in proportion to the sum of all.…”

Potential generation and path‐integral Monte Carlo in study of microscopic superfluidity

“…The microscopic version of the Andronikashvili experiment was first conducted by Grebenev et al in 1998. [8] They measured the rovibrational spectrum of OCS doped in a 4 He droplet with thousands of atoms at T 5 0.37 K. In the spectrum, the group observed a well-resolved rotational structure with a rotational inertia greater than that of a free OCS molecule.…”

Including nuclear quantum effects into highly correlated electronic structure calculations of weakly bound systems

“…In fact, spectroscopic probes of molecular impurities in helium droplets have shown that while 4 He clusters result in superfluid behavior with free-rotor-like molecular spectra, 3 He atoms behave as a normal fluid and the impurity spectra are of hindered-rotor type. 1 Since 4 He atoms are composite spinless bosons and 3 He atoms are fermionic particles with a nuclear spin equal to 1/2, one fundamental question has concerned the influence of the spin and the antisymmetry of the fermionic 3 He wave-functions in providing such different response to the molecular rotation. QuantumChemistry (QC)-like Nuclear-Orbital (NO) approaches, first introduced by Jungwirth and Krylov, 2 map the problem onto an electronic structure-like problem by considering the helium atoms as pseudo-electrons and the dopant molecule as a structured pseudo-nucleus, replacing Coulomb interactions by van der Waals He-He and He-dopant pair potentials.…”