PLANAR CLUSTERS OF RYDBERG MATTER K-N (N = 7, 14, 19, 37, 61) DETECTED BY MULTIPHOTON FRAGMENTATION TIME-OF-FLIGHT MASS-SPECTROMETRY

We report a direct observation of large planar clusters characteristic for Rydberg matter. This state of matter has low density with interat omic distances of the order of tens of nanometers. We observe the lase r multiphoton-induced fragmentation and ionization of potassium cluste rs K-N(+) with N (the magic numbers) = 7, 14, 19, 37 and 61 in process es due to 5-12 photons of 2.2 eV (564 nm) in 5 ns pulses, using time-o f-flight (TOF) mass spectrometry. The clusters are formed by desorptio n of K Rydberg atoms from a basal graphite surface, which is intercal ated by a weak molecular beam of K. The fragmentation is strongly infl uenced by the electric field used, below 4 V/cm. The efficient multiph oton fragmentation is probably due to the low rate of E-V transfer in the cluster. (C) 1998 Elsevier Science B.V. All rights reserved.