Adsorption and two-body recombination of atomic hydrogen on 3^3He-4^4He mixture films

We present the first systematic measurement of the binding energy $E_a$ of hydrogen atoms to the surface of saturated $^3$He-$^4$He mixture films. $E_a$ is found to decrease almost linearly from 1.14(1) K down to 0.39(1) K, when the population of the ground surface state of $^3$He grows from zero to $6\times10^{14}$ cm$^{-2}$, yielding the value $1.2(1)\times 10^{-15}$ K cm$^2$ for the mean-field parameter of H-$^3$He interaction in 2D. The experiments were carried out with overall $^3$He concentrations ranging from 0.1 ppm to 5 % as well as with commercial and isotopically purified $^4$He at temperatures 70...400 mK. Measuring by ESR the rate constants $K_{aa}$ and $K_{ab}$ for second-order recombination of hydrogen atoms in hyperfine states $a$ and $b$ we find the ratio $K_{ab}/K_{aa}$ to be independent of the $^3$He content and to grow with temperature.Comment: 4 pages, 4 figures, all zipped in a sigle file. Submitted to Phys. Rev. Let

Direct Microscopic Study of Doubly Polarized Atomic Hydrogen by Electron-Spin Resonance

By means of ESR in a high magnetic field the hyperfine states of a gas of spin-polarized atomic hydrogen are directly probed. This allows a direct determination of the spin-state populations and nuclear polarization. The unusual ESR line shape is attributed to field inhomogeneities. The temperature of the gas was determined by use of ESR with no indication of nonequilibrium due to Kapitza resistance. Recombination rates between hyperfine states could be determined

Exploring what works in art therapy with children with autism:Tacit knowledge of art therapists

Children with Autism Spectrum Disorders (ASD) are often referred to art therapy. To investigate what works in art therapy with these children 'tacit knowledge' of eight well experienced art therapists was explored. Promising components were arranged into the Context and Outcomes of Art Therapy (COAT) model. According to the respondents art therapy contributes with children with ASD to become more flexible and expressive, more relaxed, and more easy talking about their problems in the therapeutic setting as well as in their home situation. Considering the type of evidence in this study, further empirical research into the process and outcomes of art therapy with ASD children is strongly recommended