Analysis of Solution-Deposited Alkali Ions by Cluster Surface Collisions

Abstract

Sulfur dioxide clusters (SO2) x of mean size 〈x〉 = 1.7 × 103 collide at a velocity of 1.6 km s-1 with a metal surface that has been pretreated with dilute salt solutions containing Li+, Na+, K+, Cl-, and Br- ions in different concentrations. In the scattered gas plume, positive and negative cluster fragments of the formal composition (SO2) x (Li+, Na+, K+, SO2 -) are detected. While the amount of charge observed in the various cationic channels correlates with the concentration of the respective cations in the solutions, no cluster fragments carrying chloride or bromide anions have been observed. This indicates, that the observed free charge carriers are not formed by a direct pickup of ions from the surface. Based on the assumption that the physical state for alkali adsorbates on metal surfaces is independent of the charge state of the adsorbing precursor, the findings are explained in terms of a known charge separation effect in cluster surface collisions involving neutrally deposited alkali adsorbates.

Soft cluster-induced desorption and ionization of biomolecules—Influence of surface load and morphology on desorption efficiency

“…14, 16 In short, we used a two-chamber high vacuum apparatus (p % 10 À7 mbar) where in the first chamber the SO 2 cluster beam was produced via supersonic expansion from a pulsed nozzle (f ¼ 10 Hz, t pulse ¼ 1000 ls, nominal orifice diameter 0.5 mm). With a gas mixture of 2% SO 2 in helium at a stagnation pressure of 15 bar, the cluster beam is characterized by a narrow velocity distribution around 1.6 kms À1 and a mean cluster size of about 2 to 3 Â 10 3 molecules.…”

“…With a gas mixture of 2% SO 2 in helium at a stagnation pressure of 15 bar, the cluster beam is characterized by a narrow velocity distribution around 1.6 kms À1 and a mean cluster size of about 2 to 3 Â 10 3 molecules. 16 The target sample was mounted in the second chamber; the desorbed ions are transferred into the detection volume of the pulsed Wiley-McLaren-type time-of-flight (TOF) mass spectrometer via a biased grid placed 10 mm in front of the target. The TOF mass spectrometer itself was oriented perpendicular to the beam axis approximately 100 mm upstream from the target.…”

Molecular dynamics simulations of the micro-solvation of ions and molecules during cluster–surface collisions

“…This is no surprise as large fragments originate from the interior of the cluster [15], where the ion was placed initially. Our Na þ tagged fragments lie within the fragment size distribution of experimentally detected alkali-containing fragments [8,30], especially when considering that they would lose about 30% of their mass due to evaporative cooling [31] on their way to the detector in an experimental situation. Fig.…”

“…The details of the solvation shell around a charge carrier thus cannot be correlated to the solvation of the ion prior to impact. This also implies that so-called Ômagic numbersÕ, i.e., fragment sizes of enhanced stability, that appear in mass spectra of impact fragmented clusters [8,30] are formed during the evaporative cooling of the cluster fragments on their way to the detector.…”

Study on ion formation in electrospray droplet impact secondary ion mass spectrometry

“…A number of studies have shown that the sputtering efficiency of secondary ions is improved by increasing the mass of the primary particles. [1][2][3][4][5][6][7][8][9][10][11] Various methods have been reported for the formation of cluster ions as projectiles for cluster secondary ion mass spectrometry (SIMS). Blain et al produced cluster projectiles by 252 Cf-fission fragment-induced desorption.…”