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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 89 (1992), S. 527-530 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have prepared a large sample of spin polarized liquid 3 He- 4 He at 500 mK. Polarization is obtained by laser optical pumping, and studied by pulsed NMR. We have observed a nuclear magnetization lifetime T 1 longer than 1 hour, and an anomalously long, non linear decay of tranverse magnetization.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 89 (1992), S. 731-734 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effect of a refluxing 4 He gas facing a Rollin film on the concentration distribution of 3 He atoms is described. In some situations, a large concentration enhancement of the colder part can result. Possible applications are briefly discussed.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 97 (1994), S. 417-443 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This article comprises the first part of a study concerning the effect that a flow of gaseous4He has on the concentration distribution of3He atoms in the presence of a super fluid film. We present a simple model in which hydrodynamic effects in the gas phase (diffusion and viscosity), and local thermodynamic equilibrium with a superfluid film are considered. Results are derived and discussed for the simple case in which a heat flow is sustained along a cylindrical tube lined with a helium film. This heat flux drives a superfluid flow in the film, and a corresponding counterflow of4He in the vapour. The pressure, temperature,3He concentration, and film thickness profiles along the tube are computed. Over a wide range of conditions, a dramatic reduction of the3He concentration, a large temperature increase, and a spectacular film thinning towards hotter regions are predicted to result from a heat flow. The results of a series of experiments supporting this model will be presented in a forthcoming article.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 127 (2000), S. 443-449 
    ISSN: 1572-9540
    Keywords: polarized helium ; optical pumping ; fiber laser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report on optical pumping experiments in helium-3 using a new broad-band, all fiber laser at 1083 nm. The kinetics of polarization build-up are compared to the numerical results of an appropriate model. Effects of laser power and bandwidth are discussed.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 89 (1992), S. 135-144 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Alkali metal surfaces have been suggested not to be wetted by helium at zero temperature. Several experiments have been realized to check if these surfaces, as well as other weak binding substrates, indeed exhibits this particularly interesting property at any finite temperature. Although works are still in progress, essential results are (i) substrates non wetted by helium films do exist (ii) prewetting jumps from low to high coverage have been observed for weakly wetted ones (iii) the consequences of substrate roughness and chemical impurities are suspected to be important and remain to be assessed. These results are reviewed and discussed. Applications of those substrates for both3He and4He isotopes are considered.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 90 (1993), S. 333-333 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 21 (2002), S. 25-55 
    ISSN: 1434-6079
    Keywords: PACS. 32.60.+i Zeeman and Stark effects – 32.70.-n Intensities and shapes of atomic spectral lines – 32.80.Bx Level crossing and optical pumping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The structure of the excited 23S and 23P triplet states of 3He and 4He in an applied magnetic field B is studied using different approximations of the atomic Hamiltonian. All optical transitions (line positions and intensities) of the 1 083 nm 23S- 23P transition are computed as a function of B. The effect of metastability exchange collisions between atoms in the ground state and in the 23S metastable state is studied, and rate equations are derived, for the populations these states in the general case of an isotopic mixture in an arbitrary field B. It is shown that the usual spin-temperature description remains valid. A simple optical pumping model based on these rate equations is used to study the B-dependence of the population couplings which result from the exchange collisions. Simple spectroscopy measurements are performed using a single-frequency laser diode on the 1 083 nm transition. The accuracy of frequency scans and of measurements of transition intensities is studied. Systematic experimental verifications are made for B = 0 to 1.5 T. Optical pumping effects resulting from hyperfine decoupling in high field are observed to be in good agreement with the predictions of the simple model. Based on adequately chosen absorption measurements at 1 083 nm, a general optical method to measure the nuclear polarisation of the atoms in the ground state in an arbitrary field is described. It is demonstrated at B∼ 0.1 T, a field for which the usual optical methods could not operate.
    Type of Medium: Electronic Resource
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