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11
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0007756536
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edited by, V. Boffi, C. Cercignani, Teubner, Stuttgart
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(1986)
Proceedings of the Fifteenth Symposium on Rarefied Gas Dynamics
, vol.2
, pp. 197
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Buchenau, H.1
Götting, R.2
Scheidemann, A.3
Toennies, J.P.4
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14
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84927439660
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R. Ries and J. Gspann have also obtained evidence of the capture of Cs atoms by He clusters [Kernforschungszentrum Karlsruhe GmbH, Report No. KfK 4156, 1986 (unpublished)].
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15
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84927439659
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H. D. Meyer, dissertation, Göttingen, 1978, Max-Planck-Institut für Strömungsforschung, Bericht 5/78 (unpublished).
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16
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84927439658
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A. Scheidemann, dissertation, Göttingen, 1989, Max-Planck-Institut für Strömungsforschung, Bericht 16/1989 (unpublished).
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17
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84927439657
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The ratio of the absolute increase for the two isotopes is equal to the natural isotropic abundance ratio (9/91). A similar result is found for the increases at the Ne420 He+ and Ne422 He+ masses.
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18
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84927439648
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This suggests that the synchronous impurity signals noted previously probably arise from capture of residual gases (e.g., H2O, N2, H)2 by clusters along their flight path.
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19
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84927439646
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The lack of an observable deflection associated with capture allows us to set a rough lower bound of 2500 atoms for the size of the clusters involved. It is likely that the clusters are significantly larger than this, however (see Refs. 1, 2, and 16).
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21
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84927439644
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E. L. Knuth, W. Li, and J. P. Toennies, in Proceedings of the Sixteenth Rarefied Gas Dynamics Symposium, Pasadena, California, 1988 (to be published). This assumption is probably not accurate when the expansion enters the critical region or crosses the phase boundary.
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23
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84927439643
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With mean cluster size < N > and a constant total flux, the number of clusters is prop < N > -1. Moreover, assuming constant cluster density, a geometrical capture cross section will be prop < N > 2/3. The capture rate is then prop < N > -1/3. In this case, a local maximum in < N > will produce a local minimum in the capture rate. We note, however, that what we measure is the Ne+22-ion counting rate. Since ionization and fragmentation processes can also depend on < N > , the overall effect of a local maximum is difficult to predict.
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