Normal-Incidence Electrostatic Rydberg Atom Mirror

A Rydberg atom mirror has been designed and its operational principle tested experimentally. A supersonic expansion containing H atoms moving with a velocity of $720\mathrm{m}/\mathrm{s}$ initially propagates toward a quadrupolar electrostatic mirror. The H atoms are then photoexcited to $n=27\mathrm{Rydberg}$ states with a positive Stark shift and move in a rapidly increasing electric field. The H atom beam is stopped in $4.8\mu \mathrm{s}$, only 1.9 mm away from the photoexcitation spot, and is then reflected back. The reflection process is monitored by pulsed field ionization and imaging.

Figure 1

Panel (a) Voltage sequence used in the mirroring process. Panels (b)–(d) Voltage configurations used to (b) prepare the H atoms in Rydberg Stark states, (c) to reflect the H atoms, and (d) to field ionize the reflected atoms. The width of the electrodes in the $x$ dimension is 2 cm. The solid lines in panels (b), (c) are lines of constant electric field in steps of $25\mathrm{V}/\mathrm{cm}$ (b) and $100\mathrm{V}/\mathrm{cm}$ (c). In panel (d) equipotential lines between 850 V and 200 V in steps of 50 V are shown. The dot in panel (b) marks the photoexcitation point.

Figure 2

Panels (a), (b) TOF distributions of the ${\mathrm{H}}^{+}$ ions after deceleration periods $\tau$ of (from bottom to top) $0.6\mu \mathrm{s}$, $1.6\mu \mathrm{s}$, $2.6\mu \mathrm{s}$, $3.6\mu \mathrm{s}$, $4.6\mu \mathrm{s}$, $5.6\mu \mathrm{s}$, $6.6\mu \mathrm{s}$, $7.6\mu \mathrm{s}$, and $8.6\mu \mathrm{s}$. The solid lines are measurements with $V_4=-V_3=700\mathrm{V}$ and the dashed lines are measurements with $V_4=-V_3=0\mathrm{V}$ (“mirror off”). Panel (a) shows the experimental data and panel (b) the simulations. The origin of the time scale is chosen to be at the maximum of the TOF distribution of the $\tau =0.6\mu \mathrm{s}$ measurement. Panel (c) Comparison between the mirror on and mirror off trajectories of the central part of the atomic cloud. The (red) upper dots show the calculated trajectory of a cloud that moves with a constant velocity of $720\mathrm{m}/\mathrm{s}$. The (black) lower dots show the measured trajectory of the atomic cloud in the “mirror on” experiments. The dot size is larger than the experimental uncertainty.

Figure 3

Panel (a) Simulated phase-space diagrams of the distribution of the Rydberg atom cloud in the $z$ dimension between $t=0$ (top left corner) and $t=9\mu \mathrm{s}$ (lower left corner) in steps of $1\mu \mathrm{s}$. Panel (b) Simulated phase-space diagrams in the $y$ dimension at the same times. Panel (c) Simulated distribution of the particles within the electrodes at $t=0$, $2\mu \mathrm{s}$, $4\mu \mathrm{s}$, $6\mu \mathrm{s}$, $8\mu \mathrm{s}$, and $9\mu \mathrm{s}$. In all these graphs $z=0$ is the excitation point of the particles.

Figure 4

CCD-camera images of the ions after field ionizing the Rydberg particles in the mirror at (a) $\tau =2.6\mu \mathrm{s}$ and (b) $\tau =5.6\mu \mathrm{s}$. Each image is 25 mm long and 8 mm high. The vuv and uv laser beams propagate along the $x$ axis.