1. Extracting the magic numbers of water clusters from abundance spectra K.Hansen, Dept. of Physics, Göteborg University P.Andersson, Dept. of Chemistry, Atmospheric Science, Göteborg University E.Uggerud, Dept. of Chemistry, Universitetet i Oslo

2. Pure water clusters H + (H 2 O) n N=21 (it is ”magic”)

3. Electrospray source & TOF-MS Ion product determination Ion production (Quadrupole mass filter, off) (TOF-MS) (collision cell, empty) Transit time defines cooling time

4. abundances / smoothened abundance distribution evaporative activation energies smoothened ditto heat capacity/k B evaporative rate constant frequency factor Evaporative ensemble abundances:

5. J.Borggreen et al., Phys.Rev. A 62 (2000) 013202. Example 1: Na cluster separation energies compared with heat bath evaporation

6. L. Schweikhard et al. Eur.Phys.J.D 36 (2005) 179 Example 2: Gold clusters in Penning trap compared with modelfree data

10. Conclusions: ’Magic’ appearance of N=21 is due both to enhanced stability of 21 and reduced stability of 22. N=28, 55 appear magic because 29, 56 are anti-magic Need to understand better: Thermal properties Radiative heating

11. Z.Shi et al., JCP 99 (1993) 8009 Metastable fragmentation

12. Radiative heating Th.Schindler et al., CPL 250 (1996) 301

13. Z.Shi et al., JCP 99 (1993) 8009