Experiments to Control Atom Number and Phase-Space Density in ...

Chapter 2
Cold Atomic Gases
This dissertation is ultimately about atomic cooling, trapping, and the manip-
ulation of cold atomic ensembles. This chapter addresses the standard experimental
techniques used in cold atom experiments as well as the fundamental physical interac-
tions between atoms and electromagnetic fields relevant to these techniques.
2.1 87 Rubidium
Rubidium (Rb), being an alkali metal, has only one electron in the valence shell.
This common feature in alkali atoms gives rise to a relatively simple energy level structure
and makes alkali atoms a popular choice for cold atom experiments. The most abundant
natural isotope of rubidium is 85 Rb (nuclear spin I = 5/2), with a natural abundance of
72.17(2)%. The work in this dissertation however was performed using 87 Rb (nuclear spin
I = 3/2). 87 Rb has a half-life time of about 4.88×10 10 years and a natural abundance
of 27.83(2)%. Rubidium melts at 312.46 K and boils at 961.15 K [15].
The vapor pressure of rubidium is an important parameter for the experiment.
Fortunately the vapor pressure of rubidium is high enough that atoms can be trapped
directly from the background pressure. The vapor pressure Pv in torr for solid Rb is
given in [16] by
log10Pv = 2.881+4.857− 4215
, (2.1)
T
where T is the temperature in Kelvin. Figure 2.1 shows the vapor pressure of solid
rubidium.
Some important physical properties of 87 Rb are summarized in table 2.1. A more
complete summary of the properties of 87 Rb can be found in [17].
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