= Raman sideband cooling experiment of 1995
{c}
In 1995, <Christopher Monroe> and collaborators cooled one $^9\mathrm{Be}^+$ <ion> in a ring/endcap <Paul trap>. They used $313\ \mathrm{nm}$ <Doppler cooling> and <optical pumping> into $|F,m_F\rangle=|2,2\rangle$. Red-sideband <Raman transitions> transferred population to $|1,1\rangle$, followed by dissipative recycling. Repeating across three directions yielded a reported three-dimensional <ground state> population of about $92\%$.<Resolved-Sideband Raman Cooling of a Bound Atom to the 3D Zero-Point Energy by Christopher Monroe and others>[Monroe and others, Resolved-Sideband Raman Cooling of a Bound Atom to the 3D Zero-Point Energy, 1995, pp. 4011–4013, Fig. 1 and Table I]{ref}
A variable-frequency <Raman transition> probe, an exchange pulse and a cycling detection beam converted state populations into <fluorescence> collected through $f/2$ optics onto a position-sensitive <photomultiplier>. Red/blue asymmetry inferred motional occupation; varying probe duration tested the thermal assumption. Off-resonant processes and independently observed heating limited cooling.<Resolved-Sideband Raman Cooling of a Bound Atom to the 3D Zero-Point Energy by Christopher Monroe and others>[pp. 4012–4014, Fig. 2, Table I and final heating discussion]{ref}
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