Imaging the structure of the trimer systems (4)He3 and (3)He(4)He2

Area of Science:

• Quantum physics
• Atomic and molecular clusters
• Low-temperature physics

Background:

• Helium exhibits unique quantum phenomena, including superfluidity in its liquid phase.
• The structure of helium trimers (He3) has been debated for over 20 years, with predictions ranging from linear to triangular shapes.

Purpose of the Study:

• To experimentally determine the structure of helium trimers, specifically (4)He3 and (3)He(4)He2.
• To resolve the long-standing dispute regarding the geometric configuration of helium trimers.

Main Methods:

• Utilizing Coulomb explosion imaging of mass-selected helium clusters.
• Obtaining experimental images of the wave functions for (4)He3 and (3)He(4)He2.

Main Results:

• Experimental data suggests that the (4)He3 trimer exists as a structureless random cloud.
• The (3)He(4)He2 cluster is identified as a quantum halo state.

Conclusions:

• The study provides direct experimental evidence clarifying the ambiguous structure of helium trimers.
• Findings contribute to understanding quantum behavior in small atomic aggregates and superfluid helium.