Measurement of the Absolute Photoionization Cross Section for the 5 P _3/2 State of ⁸⁷ Rb in a Vapor Cell Magneto-optic Trap

Abstract

We report the measurement of the absolute photoionization cross section for the 5P 3/2 state of 87 Rb at wavelength of 473 nm, which results in the photoelectron energies of 33 meV above the ionization threshold, using cold atoms confined in a vapor-loaded magneto-optical trap. The 87 Rb 5P 3/2 photoionization cross section at 473 nm is determined to be 𝜎 PI = 10.5 ± 2.2 Mb. Considering the spatial distribution of the trapped atoms, the average intensity 𝐼 PI of the ionization laser seen by an atom in the MOT instead of ionizing laser intensity 𝐼 PI is used in our calculations for the photoionization cross sections. The excited state fraction is also accurately estimated using the latest experimental result.

Photoionization of optically trapped ultracold atoms with a high-power light-emitting diode

“…The measured cross sections covered a spectral range from 406.1 nm to 476.5 nm. [17][18][19]21 Our measured cross section compares favourably to the values measured in Refs. 17-19 and the calculations in Ref.…”

“…For the following analysis, we assume σ to be constant over the LED spectrum. Previous measurements [17][18][19] and calculations 20 only show a small variation below 10% of the cross section over this spectral range justifying this assumption. The effective cross section can be determined from the total number of trapped atoms N(t) using a simple rate equation model: 21…”

Temperature of the Remaining Cold Atoms after Two-Step Photoionization in an 87 Rb Vapor Cell Magneto-Optical Trap

“…The details of the experimental apparatus were described in our previous work. [11] About 5 × 10 7 87 Rb atoms are trapped, the density of cold atoms is about 2-4×10 10 cm −3 , and the 1/𝑒 half waist of the cold atomic cloud is measured to be about 1 mm. The total number of cold atoms is directly measured in situ by atomic fluorescence using a CCD camera.…”

“…Note that the ionizing laser intensity is the averaged intensity Ī𝑃 𝐼 seen by the cold atomic cloud with a Gausdistribution. [11,13] The number and temperature of the remaining cold atoms after photoionization can be measured by atomic fluorescence and the time-offlight method, respectively, as discussed above. The experimental errors in this work mainly result from the following factors: the statistical uncertainties, the uncertainties in determining the size of the cold atomic cloud, the uncertainties of frequency calibration resulting from the frequency jitter ∼1 MHz of the cooling/trapping laser, the repumping laser and the probe laser, and the uncertainties of the ionizing laser intensity.…”

The Inversionless Amplification in a Tripod System of 87 Rb Atoms in a Magneto-optical Trap

“…Details of the apparatus were described in our previous work. [9] Briefly, three pairs of cooling/trapping and re-pumping beams with 𝜎 + and 𝜎 − circularly polarized were provided by two frequency-stabilized diode lasers, respectively, and the re-pumping beams were overlapped with the cooling/trapping beams. An inhomogeneous magnetic field was created by a pair of anti-Helmholtz coils.…”