Guiding of Rydberg atoms in a high-gradient magnetic guide

We study the guiding of ${}^{87}$Rb 59$D$${}_{5/2}$ Rydberg atoms in a linear, high-gradient, two-wire magnetic guide. Time-delayed microwave ionization and ion detection are used to probe the Rydberg atom motion. We observe guiding of Rydberg atoms over a period of 5 ms following excitation. The decay time of the guided-atom signal is about five times that of the initial state. We attribute the lifetime increase to an initial phase of $l$-changing collisions and thermally induced Rydberg-Rydberg transitions. Detailed simulations of Rydberg-atom guiding reproduce most experimental observations and offer insight into the internal-state evolution.

Figure 1

Schematic of the excitation and detection region in the two-wire magnetic guide. The guided atoms (small red dot) travel between the guide wires, where they are excited into Rydberg levels with two lower (780 nm, dashed red arrow) and one upper (480 nm, solid blue arrow) transition beams. The Rydberg atoms are detected by microwave ionization. With the guide support grounded and the guard tube at $-1.4$ kV, ions are directed upward to a microchannel plate (MCP), where counts are recorded with both spatial and temporal resolution.

Figure 2

(a) MS trace, at $t_d=1.5$ ms. MCP image with a delay time of $t_d=1.5$ ms, with (b) camera on throughout the experimental cycle and (c) camera gated over the microwave ionization signal. The black square indicates 1 mm${}^2$ in the image plane. The images exhibit a remnant of laser light penetrating through the MCP and phosphor screen. (d) Profiles of each from the regions indicated by the dashed boxes.

Figure 3

(a) MS traces as a function of delay time $t_d$. (b) Gated MCP images as a function of $t_d$. The brightness scale of each picture is optimized separately for clarity.

Figure 4

Fraction of Rydberg atoms remaining vs delay time $t_d$ from experiment (squares) and simulation with $l$ mixing (triangles) and without $l$ mixing (circles). The parentheses indicate points where a significant portion of the experimental signal is blocked from detection. The dashed line shows an extrapolation of the experimental curve based on the assumption that the Rydberg signal decay time does not change after 4 ms, where the signal is partially blocked.