BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-3185
DTSTART:20140228T213000Z
DURATION:PT1H0M0S
DTSTAMP:20260309T180322Z
LAST-MODIFIED:20140225T143154Z
LOCATION:2241 Chamberlin Hall (coffee at 4:30 pm)
SUMMARY:A single Rydberg electron in a Bose-Einstein Condensate\, Phys
 ics Department Colloquium\, Prof. Tilman Pfau\, University of Stuttgar
 t
DESCRIPTION:Electrons attract polarizable atoms via a 1/r^4 potential.
  For slow electrons the scattering from that potential is purely s-wav
 e and can be described by a Fermi pseudopotential. To study this inter
 action Rydberg electrons are well suited as they are slow and trapped 
 by the charged nucleus. In the environment of a high pressure discharg
 e Amaldi and Segre\, already in 1934 observed a lineshift proportional
  to the scattering length [1]\, which was first introduced to explain 
 their findings.<br>
\nAt ultracold temperatures and Rydberg states wit
 h medium size principle quantum numbers n\, one or two ground state at
 oms can be trapped in the meanfield potential created by the Rydberg e
 lectron\, leading to so called ultra-long range Rydberg molecules [2].
  These molecules can show a linear Stark effect corresponding to a per
 manent dipole moment [3]\, which if seen from a standpoint of traditio
 nal molecular physics is surprising.<br>
\nAt higher Rydberg states th
 e spatial extent of the Rydberg electron orbit is increasing. For prin
 cipal quantum numbers n in the range of 100-200 and typical BEC densit
 ies\, up to several ten thousand ground state atoms are located inside
  one Rydberg atom\, leading again to a density dependent energy shift 
 of the Rydberg state. This allows\, together with the strong van-der-W
 aals blockade\, to excite only one single  Rydberg atom in a condensat
 e. We excite a Rydberg electron with n upto 202 in the BEC\, the size 
 of which becomes comparable to the size of the BEC. We study their lif
 e time in the BEC and the coupling between the electron and phonons in
  the BEC [3]. So the single electron that we prepare in a quantum gas 
 allows nicely to study the transition from  two- to few- to many-body 
 interaction.<br>
\nAs an outlook\, the trapping of a full condensate i
 nside a Rydberg atom of high principal quantum number and the imaging 
 of the Rydberg electron's wavefunction by its impact onto the surround
 ing ultracold cloud seem to be within reach.<br>
\n<br>
\n[1] E. Amald
 i and E. Segre\, Nature 133\, 141 (1934)<br>
\n<br>
\n[2] C. H. Greene
 \, et al. PRL. 85\, 2458 (2000)\; V. Bendkowsky et al.\, Nature 458\, 
 1005 (2009)<br>
\n[3] W. Li\, et al.\, Science 334\, 1110 (2011)<br>
\
 n[4] J . B. Balewski\, A. T. Krupp\, A. Gaj\, D. Peter\, H. P. Büchle
 r\, R. Löw\, S. Hofferberth\, T. Pfau\, Nature 502\, 664 (2013)<br>
\
 n
URL:https://www.physics.wisc.edu/events/?id=3185
END:VEVENT
END:VCALENDAR