Thermal detection of ESR on spin-polarized hydrogen: Study of surface recombination

Mertig, Michael; Tjukanov, E.; Vasilyev, S. A.; Katunin, Andrzej; Jaakkola, S.

doi:10.1007/bf00753836

Cited by 7 publications

(6 citation statements)

References 22 publications

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“…yields E a ͞k 1.01͑3͒ K and K ab 1.8͑8͒ 3 10 29 p T cm 2 K 21͞2 s 21 (in B 0 4.57 T), in agreement with data given elsewhere [7,9,12].…”

supporting

confidence: 89%

mentioning

confidence: 99%

“…2) is detected via its energy yield using a carbon bolometer [9,11,12] placed in the buffer volume (V 4.5 cm 3 ). The bolometer response is calibrated against a temperature controller and a 128 GHz (ambient field B 0 4.57 T) ESR spectrometer [9,12]. The use of the bolometer is based on the observations [11,13,14] that only of order 1% of D is released locally at the recombination site.…”

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confidence: 99%

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Observation of Quasicondensate in Two-Dimensional Atomic Hydrogen

et al. 1998

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We have performed magnetic compression experiments with the two-dimensional gas of hydrogen atoms on liquid 4 He at T 120 200 mK. For 2D phase-space densities higher than 3, the probability of three-body dipole recombination is observed to decrease gradually by an order of magnitude in comparison to its low-density value K bbb 8.4͑3.5͒ 3 10 225 cm 4 s 21 . This is attributed to local coherence developing in a 2D quasicondensate. We have also determined the value U͞k 5.1͑5͒ 3 10 215 K cm 2 for the mean-field energy of the gas. [S0031-9007(98)07787-4] PACS numbers: 03.75.Fi, 05.30.Jp, 67.65. + z, 68.35.Rh In addition to the occupation of a single quantum state, a Bose-Einstein condensate (BEC) is characterized by long-range order or, equivalently, global coherence. The concept of quasicondensate (QC) has been introduced [1] for the lesser known situation where a boson system is coherent only locally. Having similar particle interactions, BEC and QC would be hardly distinguishable by virtue of properties related to inelastic [2,3] or elastic [4] collisions. However, the difference is transparent in spatially uniform two-dimensional (2D) system where a BEC cannot exist at finite temperature T but a QC can.In fact, a QC may appear due to interactions which suppress density fluctuations and therefore allow the 2D system to be described by a single wave function. Although the phase of the function fluctuates spatially and thus thwarts a long-range order [1], the phase coherence persists within a finite length L~exp͑sl 2 ͒ [2]. Here, l p 2ph 2 ͞mkT is the de Broglie wavelength, s is the 2D gas density, and m is the particle mass. For T ! 0 the "local BEC" regions of size L tend to extend throughout the sample and the QC turns into a "true" condensate.The appearance of a QC is to be expected when the interaction energy becomes comparable with the kinetic energy, sU ϳ kT . Here, U 4ph 2 j͞m is the mean-field parameter for elastic interactions and j is a dimensionless interaction strength. It is known that at T 0 the ratio of densities of above-condensate and condensate particles is s 0 ͞s 0 ഠ j [5]. Therefore a QC may manifest itself preferably in weakly interacting (low-j) systems.This Letter reports on the first experimental evidence for a quasicondensate in 2D atomic hydrogen gas, where we have observed a significant reduction in three-body recombination probability [2,6]. Hydrogen atoms on liquid 4 He surface occupy a single bound state with low adsorption energy, E a ͞k Ӎ 1.0 K [7]. The H adatoms are localized quite far, 8 Å, from the liquid and their out-of-plane delocalization length, l h͞ p 2E a m Ӎ 5 Å, is large compared with, e.g., the 3D scattering length a 0 0.72 Å. Thus adsorbed hydrogen may be also regarded as quasi-2D in the sense that it obeys 2D statistics while particle interactions are three dimensional [2]. It may be shown [2] that j ഠ a 0 ͞l and consequently a QC in hydrogen on 4 He may be observed at sl 2 * l͞2a 0 Ӎ 3.5.It is not easy to achieve a high degree of quantum degeneracy, i.e., high s at ...

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“…yields E a ͞k 1.01͑3͒ K and K ab 1.8͑8͒ 3 10 29 p T cm 2 K 21͞2 s 21 (in B 0 4.57 T), in agreement with data given elsewhere [7,9,12].…”

supporting

confidence: 89%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Observation of Quasicondensate in Two-Dimensional Atomic Hydrogen

et al. 1998

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“…(1), we see that VCE is sensitive at large a and w. We operate our VCE at a and w as large as possible on conditions that its linearity is maintained and heating of the cell is negligible. An aquadag film bolometer [13] in the cell allows us to sense the heating. In this experiment V DC = 90 V. VCE is operated at w p / 2 880 = Hz and the driving voltage of the piezo actuator 5.0 V peak-to-peak.…”

Section: Apparatusmentioning

confidence: 99%

Electron attachment to atomic hydrogen on the surface of liquid He4

Arai

Yayama

Kono

2008

Low Temperature Physics

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We demonstrate a possibility that helium surface electrons at cryogenic temperatures can be used as a new source of very low energy electrons. Since both electrons (e -) and hydrogen atoms (H) are bound on liquid helium surface, two-dimensional mixture gas of these two species is available on the surface. We found that low energy collision of e -and H drives electron attachment to form a negative hydrogen ion (H -) in the mixture. From our temperature dependence measurement of the reaction rate, it was found that another H atom participate in the reaction. Namely, the reaction is expressed as H + H + e -® H -+ H. Possible reaction mechanisms are discussed in terms of direct three-body process and dissociative attachment process. Measurements in applied magnetic field (B) show that the reaction rate coefficient is suppressed as~-B 2 . This implies that electron spin singlet collision is relevant for electron attachment. PACS: 67.63.Gh Atomic hydrogen and isotopes; 67.25.-k 4 He; 68.03-g Gas-liquid and vacuum-liquid interfaces.

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“…This predetermines the operating frequency to the mm-wave range. [1][2][3][4] A specific feature of ESR on H↓ is the resonance-induced destruction of the sample. Atoms with flipped spins promptly recombine in collisions with other atoms.…”

Section: Introductionmentioning

confidence: 99%

Cryogenic 2 mm wave electron spin resonance spectrometer with application to atomic hydrogen gas below 100 mK

Vasilyev

Järvinen

Tjukanoff

et al. 2004

Review of Scientific Instruments

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We describe a 128 GHz electron-spin-resonance spectrometer based on heterodyne detection with double frequency conversion utilizing cryogenic Schottky-diode mixers. Together with other mm-wave components installed into a dilution refrigerator cryostat, the mixers comprise a bridge operating at 1.5 K. A miniature Fabry-Perot resonator is used to detect samples of bulk and surface-adsorbed atomic hydrogen gas at temperatures below 100 mK. The sensitivity is 2 ϫ10 9 spins/Gauss at the excitation power of 20 pW.

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Thermal detection of ESR on spin-polarized hydrogen: Study of surface recombination

Cited by 7 publications

References 22 publications

Observation of Quasicondensate in Two-Dimensional Atomic Hydrogen

Observation of Quasicondensate in Two-Dimensional Atomic Hydrogen

Electron attachment to atomic hydrogen on the surface of liquid He4

Cryogenic 2 mm wave electron spin resonance spectrometer with application to atomic hydrogen gas below 100 mK

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