Speaker
Dr
Stephen Hogan
(University College London)
Description
In its triplet ground state the positronium (Ps) atom self-annihilates on a timescale of 142 ns [1]. This short lifetime rules out the possibility of performing tests of antimatter gravity using ground state Ps atoms. However, when excited to Rydberg states with high principal quantum number [2], direct self-annihilation can become negligible and the Ps lifetime is dominated by radiative decay. The radiative lifetimes of Rydberg states of Ps are twice as long as those of states with the same value of n in the hydrogen atom, as are the maximal induced electric dipole moments. The combination of these long radiative lifetimes, large electric dipole moments, and the low mass of the Ps atom, makes Rydberg Ps ideally suited to focussing, deceleration and trapping using inhomogeneous electric fields (see, e.g., [3]).
In this talk, experiments in which Rydberg-Stark states of Ps with electric dipole moments as large as 840 D have been prepared will be presented [4]. Experimental methods, presently developed for the manipulation of beams of helium Rydberg atoms [5], but which may be extended to guide and confine Rydberg Ps for gravity measurements, will also be discussed along with possible spectroscopic tests of antimatter gravity with Rydberg Ps.
[1] R. S. Vallery, P.W. Zitzewitz, and D.W. Gidley, Phys. Rev. Lett. 90, 203402 (2003).
[2] D. B. Cassidy, T. H. Hisakado, H. W. K. Tom, and A. P. Mills, Jr., Phys. Rev. Lett. 108, 043401 (2012).
[3] S. D. Hogan, M. Motsch, and F. Merkt, Phys. Chem. Chem. Phys., 13, 18705 (2011).
[4] T. E. Wall, A. M. Alonso, B. S. Cooper, A. Deller, S. D. Hogan, and D. B. Cassidy, Phys. Rev. Lett., 114, 173001 (2015).
[5] H. Ko and S. D. Hogan, Phys. Rev. A, 89, 053410 (2014).
Author
Dr
Stephen Hogan
(University College London)
