Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Pauli Blocking of Collisions in a Quantum Degenerate Atomic Fermi Gas



B. L. DeMarco, S Papp, D S. Jin


We have produced an interacting quantum degenerate Fermi gas of atoms composed of two spin-states of magnetically trapped 40K. The relative Fermi energies are adjusted by controlling the populations in each spin-state. Thermodynamic measurements reveal a resulting imbalance in the mean energy per particle between the two species, which is a factor of 1.4 at our lowest temperature. This imbalance of energy comes from a suppression of collisions between atoms in the gas due to the Pauli exclusion principle. Through measurements of the thermal relaxation rate we have directly observed this Pauli blocking as a factor of 2 reduction in the effective collision cross section in the quantum degenerate regime.
Physical Review Letters


fermi gas, Pauli blocking


DeMarco, B. , Papp, S. and Jin, D. (2001), Pauli Blocking of Collisions in a Quantum Degenerate Atomic Fermi Gas, Physical Review Letters (Accessed February 26, 2024)
Created June 1, 2001, Updated February 17, 2017