Direct observation of interatomic Coulombic decay and subsequent ion-atom scattering in helium nanodroplets

Abstract

We report on the experimental observation of Interatomic Coulombic Decay (ICD) in pure 4 He nanoclusters of mean sizes between N~5000-30000 and the subsequent scattering of energetic He + fragments inside the neutral cluster by using Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS). ICD is induced in He clusters by using VUV light of hν = 67 eV from the BESSY II synchrotron. The electronic decay creates two neighboring ions in the cluster at a well-defined distance. The measured fragment energies and angular correlations show that a main energy loss mechanism of these ions inside the cluster is a single hard binary collision with one atom of the cluster. † Electronic address: doerner@atom.uni-frankfurt.de

Interatomic and Intermolecular Coulombic Decay

“…In larger clusters collisions, fragmentation into complexes that include neutrals, and postdecay nuclear dynamics all lead to a blurring of the sought-for ion signal. 258 , 259 Pure spectroscopy of energetic ions is capable to detect ICD only in some favorable cases and has mostly been superseded by powerful coincidence methods, which will be described in the next section.…”

“…Early experiments on ICD using the COLTRIMS technique can be found, for example, in refs ( 2 , 8 , 15 , 16 , 29 , 57 , 58 , 60 , 187 − 189 , 198 , 215 , and 296 − 303 ); later work in refs ( 23 , 28 , 196 , 203 , 205 , 245 , 247 , 248 , and 304 − 315 ); and most recent work in refs ( 54 , 107 , 192 , 201 , 249 , 250 , 259 , and 316 − 324 )…”

“…Subsequent work by Wiegandt et al showed that the main energy loss mechanism is a single hard binary collision with another atom of the cluster. 259 The momentum resolving ion data showed, furthermore, a direct fingerprint of elastic scattering events between the ions and the surrounding atoms.…”

Time-resolved Ultrafast Interatomic Coulombic Decay in Superexcited Sodium-doped Helium Nanodroplets

“…Superfluid helium (He) nanodroplets are ideal model systems to study electronic relaxation and ionization dynamics, not only because of the extremely weak interatomic binding of the He atoms to each other and to dopants, but also because the simple electronic structure of the He atom greatly facilitates the interpretation of electron spectra. [11][12][13] ICD and ICD-like decay mechanisms have been studied in both pure He droplets [13][14][15][16][17] and in droplets doped with various metal atoms and molecules. [18][19][20][21][22][23][24][25][26] In the case where atomic or molecular impurities are ionized through resonant valence-shell excitation of the He droplet, the ICD process resembles what traditionally has been termed Penning ionization by analogy to collisional ionization in a crossed beam experiments involving metastable rare gas atoms.…”

Density functional study of the variants of inter-Coulombic decay resonances in the photoionization of Cl@C60

“…Furthermore, charged particle impact, such as pulsed electron guns [6] or alpha-particle impact [7] have also been used. ICD signatures are probed by traditional methods of electron [8] and ion [9] spectroscopy, including various coincidence techniques [10]. Access to time-resolved ICD dynamics has also been possible by the contemporary pump-probe approaches [5,11], specifically, by light field streaking techniques [12].…”