| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1988: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1987: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
Drift tube of an injected-ion drift tube mass spectrometer was cooled with liquid helium for studing ion-molecule reactions at very low temperatures. By injecting ions X^+ (X=He, Ne, Ar, Kr) into the drift tube filled with helium gas of the pressure ranging from 0.01 to 0.06 Torr at the temperature of about 4.5 K, helium cluster ions (XHE_n)^+ were observed with the largest size of n=14.
Generally, the binding energy of a cluster decreases with increasing size. Therefore, when the drift field strength, the effective temperature of the drifting ions, in the drift tube is high, only the clusters having a larger binding energy than the effective temperature of the drifting ions may be detected. We measured a number of mass spectra by varing the electric field strength and determined the disappearance drift field strength of the cluster (XHe_n)^+. By this means, we were able to obtain an information about the stability of the clusters and determined the magic numbers. For the case X=He, the magic numbers n=1, 2, 9, 13 were observed. On the other hand, the differnt ones were observed for Ne and Ar.
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