Abstract:We present a method for determining the depth of an atomic or molecular trap of any type. This method relies on a measurement of the trap loss rate induced by collisions with background gas particles. Given a fixed gas composition, the loss rate uniquely determines the trap depth. Because of the "soft" long-range nature of the van der Waals interaction, these collisions transfer kinetic energy to trapped particles across a broad range of energy scales, from room temperature to the microkelvin energy scale. The… Show more
“…This value is necessarily less than but within an order of magnitude of the total cross section due to the finite trap depth. From previous works on trap loss rates of cold atoms due to collisions with foreign gases [35,36], it is known that the trap loss rate varies quite strongly with trap depth especially near the energy scale for quantum diffractive collisions, ϵ d ¼ 4πℏ 2 =mσ T , where m is the mass of trapped particles and σ T is the total collision cross section [37]. This energy scale is on the order of ∼100 mK for the present case.…”
Section: Prl 118 093201 (2017) P H Y S I C a L R E V I E W L E T T Ementioning
confidence: 71%
“…Under such conditions, the number of trapped radicals, N CH 3 , may obey a first order differential equation dN CH 3 =dt ¼ −ð1=τÞN CH 3 , where the lifetime, τ, is inversely proportional to the average of the product of the cross section, σ, velocity, v, and the density, n, of background gas particles [35]. The measurement of background gases by a residual gas analyzer revealed that the major component of the background gas in our vacuum chamber was H 2 (or H) with some N 2 as a minor component (less than 1=3 of H 2 ).…”
Section: Prl 118 093201 (2017) P H Y S I C a L R E V I E W L E T T Ementioning
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“…This value is necessarily less than but within an order of magnitude of the total cross section due to the finite trap depth. From previous works on trap loss rates of cold atoms due to collisions with foreign gases [35,36], it is known that the trap loss rate varies quite strongly with trap depth especially near the energy scale for quantum diffractive collisions, ϵ d ¼ 4πℏ 2 =mσ T , where m is the mass of trapped particles and σ T is the total collision cross section [37]. This energy scale is on the order of ∼100 mK for the present case.…”
Section: Prl 118 093201 (2017) P H Y S I C a L R E V I E W L E T T Ementioning
confidence: 71%
“…Under such conditions, the number of trapped radicals, N CH 3 , may obey a first order differential equation dN CH 3 =dt ¼ −ð1=τÞN CH 3 , where the lifetime, τ, is inversely proportional to the average of the product of the cross section, σ, velocity, v, and the density, n, of background gas particles [35]. The measurement of background gases by a residual gas analyzer revealed that the major component of the background gas in our vacuum chamber was H 2 (or H) with some N 2 as a minor component (less than 1=3 of H 2 ).…”
Section: Prl 118 093201 (2017) P H Y S I C a L R E V I E W L E T T Ementioning
The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.
“…The steady state number of atoms in the MOT is In the regime where β n ss is small compared to the losses due to background vapor, Γ≃ (a few s −1 to 0.01 s −1 ), Eq. (10) can be approximated by [33] Nt N ss 1 − e −γt .…”
Section: Methodsmentioning
confidence: 99%
“…For rubidium atoms in a magnetic trap, the trap depth can readily be estimated based on the magnetic field gradient, the magnetic properties of the trapped species, and the geometry of the vacuum cell [33]. That is, atoms in a magnetic trap with sufficient energy to reach the wall of the vacuum container will be heated via contact with the wall and escape the trap.…”
Section: Evaluating the Relationship Between V C And V Ementioning
confidence: 99%
“…When this energy is sufficient for the atoms to escape the trap, loss is observed, providing a measure of the average MOT depth. The method employed is described fully in [33] and, for convenience, outlined in Appendix A of this paper. Table 1 summarizes the cooling laser settings (detunings and intensities) for each MOT measured along with deduced trap depths.…”
Section: A Dependence Of the Loading Rate On Trap Depthmentioning
We study the dependence of the particle loading rate of a rubidium vapor cell magneto-optic trap (MOT). Using a trap depth determination of the MOT that relies on measurements of loss rates during optical excitation of colliding atoms to a repulsive molecular state, we experimentally determine the MOT escape velocity and show that the loading rate scales with escape velocity to the fourth power, or, equivalently, with the square of the trap depth. We also demonstrate that the loading rate is directly proportional to the background rubidium density. We thus experimentally confirm the loading rate model used in the literature since the invention of the MOT. In addition to confirming this long-standing conjecture, we show that the loading rate dependence can be used to reliably infer the trap depth and to tune the relative depth of a MOT (i.e., capture and escape velocities) when the background density is held fixed. The measurements have allowed an experimental determination of the relationship between capture and escape velocities in our MOTs of v c 1.290.12v e .
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