Metastable helium: a new determination of the longest atomic excited-state lifetime
Date
2009
Authors
Hodgman, Sean
Dall, Robert
Byron, Lesa
Buckman, Stephen
Truscott, Andrew
Baldwin, Kenneth
Journal Title
Journal ISSN
Volume Title
Publisher
American Physical Society
Abstract
Exited atoms may relax to the ground state by radiative decay, a process which is usually very fast (of order nanoseconds). However, quantum-mechanical selection rules can prevent such rapid decay, in which case these “metastable” states can have lifetimes of order seconds or longer. In this Letter, we determine experimentally the lifetime of the longest-lived neutral atomic state—the first excited state of helium (the 2 3S1 metastable state)—to the highest accuracy yet measured. We use laser cooling and magnetic trapping to isolate a cloud of metastable helium (He*) atoms from their surrounding environment, and measure the decay rate to the ground 1 1S0 state via extreme ultraviolet (XUV) photon emission. This is the first measurement using a virtually unperturbed ensemble of isolated helium atoms, and yields a value of 7870(510) seconds, in excellent agreement with the predictions of quantum electrodynamic theory.
Description
Keywords
Keywords: Atomic state; Decay rate; Excited-state lifetime; Exited atoms; Extreme ultraviolets; First excited state; Helium atom; Magnetic trapping; Meta-stable state; Metastable helium; Photon emissions; Quantum electrodynamics; Quantum mechanical; Radiative decay
Citation
Physical Review Letters 103.5 (2009): 053002/1-4
Collections
Source
Physical Review Letters
Type
Journal article
Book Title
Entity type
Access Statement
Open Access
License Rights
Restricted until
Downloads
File
Description