Photoionization by blackbody radiation

Spencer, William P.; Vaidyanathan, A.; Kleppner, Daniel; Ducas, Theodore W.

doi:10.1103/physreva.26.1490

Cited by 58 publications

(76 citation statements)

References 11 publications

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“…al. [24]. And this supports the suggestion that black-body photoionization plays a role in the initial ionization.…”

Section: Rydberg Gas Evolution To Plasmasupporting

confidence: 75%

External Control of Electron Temperature in Ultra-Cold Plasmas

Wilson¹,

Tate²

2008

AIP Conference Proceedings

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This thesis discusses progress towards achieving external control of the electron temperature and the Coulomb coupling parameter of ultra-cold plasmas.Using a Littman dye laser, we create the plasma by partially photoionizing a dense, cold sample of rubidium atoms in a magneto-optical trap (MOT). At a controllable time delay, we excite neutral atoms in the plasma to a specific Rydberg state using a narrow bandwidth pulsed dye laser. We have made progress towards optimizing and quantifying the achievable Rydberg atom density by using mm-wave spectroscopy to control the evolution of a cold dense Rydberg sample to plasma and have also begun preliminary investigations of plasma electron temperature measurements.i

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“…al. [24]. And this supports the suggestion that black-body photoionization plays a role in the initial ionization.…”

Section: Rydberg Gas Evolution To Plasmasupporting

confidence: 75%

External Control of Electron Temperature in Ultra-Cold Plasmas

Wilson¹,

Tate²

2008

AIP Conference Proceedings

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“…the photoabsorption cross section of a Rydberg state with energy −E R for photons of energy E ␥ [19,20]. Similarly, E ␥ may be calculated using…”

Section: Fig 2 (A)mentioning

confidence: 99%

Evolution dynamics of a dense frozen Rydberg gas to plasma

Noel

Robinson

et al. 2004

Phys. Rev. A

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Dense samples of cold Rydberg atoms have previously been observed to spontaneously evolve to a plasma, despite the fact that each atom may be bound by as much as 100 cm −1 . Initially, ionization is caused by blackbody photoionization and Rydberg-Rydberg collisions. After the first electrons leave the interaction region, the net positive charge traps subsequent electrons. As a result, rapid ionization starts to occur after 1 s caused by electron-Rydberg collisions. The resulting cold plasma expands slowly and persists for tens of microseconds. While the initial report on this process identified the key issues described above, it failed to resolve one key aspect of the evolution process. Specifically, redistribution of population to Rydberg states other than the one initially populated was not observed, a necessary mechanism to maintain the energy balance in the system. Here we report new and expanded observations showing such redistribution and confirming theoretical predictions concerning the evolution to a plasma. These measurements also indicate that, for high n states of purely cold Rydberg samples, the initial ionization process which leads to electron trapping is one involving the interactions between Rydberg atoms.

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“…These measurements are complementary to recent all-optical measurements of the lifetimes of selected nl Rydberg states following excitation of ultracold atoms in MOT, which reveal the decay of the initially prepared Rydberg states of Rb with principal quantum numbers in the range 30-40 by fluorescence, blackbody-radiation-induced and collisional processes [31] and to earlier studies of the influence of blackbody radiation, in particular ionization, on the lifetimes and other properties of Rydberg states of atoms (see, e.g., Refs. [21][22][23][24][25][26][27][28][29], and [2] and references therein) In an effort to understand how the different radiative or collisional processes affect the evolution of Rydberg atom population and induce losses of atoms and molecules from the traps, we have successively extended the initial deceleration and trapping experiments by (i) deflecting the Rydberg atoms and molecules from the beam axis before loading them into off-axis traps in order to suppress collisions with other atoms and molecules in the beam [36], (ii) installing successive thermal shields around the traps and thermalizing these shields to progressively lower temperatures, down to below 10 K, (iii) comparing the behavior of atomic and molecular Rydberg states in experiments carried out on H atoms and H 2 molecules [37], and (iv) trying to model the relevant radiative and collisional processes.…”

Section: Introductionmentioning

confidence: 99%

“…Blackbody radiation can therefore efficiently stimulate emission or absorption processes and, in some cases, even can be the primary source of decay. The influence of blackbody radiation on the behavior of Rydberg states is well known and has been extensively investigated experimentally and theoretically [2,[21][22][23][24][25][26][27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

Seiler¹,

Agner²,

Pillet³

et al. 2016

J. Phys. B: At. Mol. Opt. Phys.

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Supersonic beams of hydrogen atoms, prepared selectively in Rydberg-Stark states of principal quantum number n in the range between 25 and 35, have been deflected by 90 ○ , decelerated and loaded into off-axis electric traps at initial densities of ≈ 10 6 atoms/cm −3 and translational temperatures of 150 mK. The ability to confine the atoms spatially was exploited to study their decay by radiative and collisional processes. The evolution of the population of trapped atoms was measured for several milliseconds in dependence of the principal quantum number of the initially prepared states, the initial Rydberg-atom density in the trap, and the temperature of the environment of the trap, which could be varied between 7.5 K and 300 K using a cryorefrigerator. At room temperature, the population of trapped Rydberg atoms was found to decay faster than expected on the basis of their natural lifetimes, primarily because of absorption and emission stimulated by the thermal radiation field. At the lowest temperatures investigated experimentally, the decay was found to be multiexponential, with an initial rate scaling as n −4 and corresponding closely to the natural lifetimes of the initially prepared Rydberg-Stark states. The decay rate was found to continually decrease over time and to reach an almost n-independent rate of more than (1 ms) −1 after 3 ms. To analyze the experimentally observed decay of the populations of trapped atoms, numerical simulations were performed which included all radiative processes, i.e., spontaneous emission as well as absorption and emission stimulated by the thermal radiation. These simulations, however, systematically underestimated the population of trapped atoms observed after several milliseconds by almost two orders of magnitude, although they reliably predicted the decay rates of the remaining atoms in the trap. The calculations revealed that the atoms that remain in the trap for the longest times have larger absolute values of the magnetic quantum number m than the optically prepared RydbergStark states, and this observation led to the conclusion that a much more efficient mechanism than a purely radiative one must exist to induce transitions to Rydberg-Stark states of higher m values. While searching for such a mechanism, we discovered that resonant dipole-dipole collisions between Rydberg atoms in the trap represent an extremely efficient way of inducing transitions to states of higher m values. The efficiency of the mechanism is a consequence of the almost perfectly linear nature of the Stark effect at the moderate field strengths used to trap the atoms, which permits cascades of transitions between entire networks of near-degenerate Rydberg-atom-pair states. To include such cascades of resonant dipole-dipole transitions in the numerical simulations, we have generalized the two-state Förster-type collision model used to describe resonant collisions in ultracold Rydberg gases to a multi-state situation. It is only when considering the combined effects of collisional and radiative pr...

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Photoionization by blackbody radiation

Abstract: We have measured the blackbody photoionization rate from the 17d state of sodium as a function of temperature from 90 to 300 K. The experimental rates, which vary by a factor greater than one hundred over this temperature range, are in good agreement with our theoretical values.

Cited by 58 publications

References 11 publications

External Control of Electron Temperature in Ultra-Cold Plasmas

External Control of Electron Temperature in Ultra-Cold Plasmas

Evolution dynamics of a dense frozen Rydberg gas to plasma

Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

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