In the secondary ion mass spectrometry (SIMS) of organic substances, the molecular weight of the intact ions currently detectable is at best only as high as 1000 Da, which for all practical purposes prevents the technique from being applied to biomaterials of higher mass. We have developed SIMS instrumentation in which the primary ions were argon cluster ions having a kinetic energy per atom, controlled down to 1 eV. On applying this instrumentation to several peptides and proteins, the signal intensity of fragment ions was decreased by a factor of 10(2) when the kinetic energy per atom was decreased below 5 eV; moreover, intact ions of insulin (molecular weight (MW): 5808) and cytochrome C (MW: 12 327) were detected without using any matrix. These results indicate that fragmentation can be substantially suppressed without sacrificing the sputter yield of intact ions when the kinetic energy per atom is decreased to the level of the target's dissociation energy. This principle is fully applicable to other biomolecules, and it can thus be expected to contribute to applications of SIMS to biomaterials in the future.

The oxidation of Cu{100} with a hyperthermal O2 molecular beam (HOMB) was investigated using x-ray photoemission spectroscopy in conjunction with a synchrotron light source. The efficiency of oxidation with HOMB is higher than that with ambient thermal O2. Further oxidation under oxygen coverage (Θ)⩾0.5 ML occurs rather inefficiently even for the 2.3-eV-HOMB irradiation. We found that such slow oxidation of Cu corresponding to the initial stage of the Cu2O formation can be interpreted in terms of a collision-induced-absorption mechanism. The kinetics of the dissociative adsorption under Θ⩽0.5 ML is well described using the first-order kinetics in a simple Langmuir-type adsorption model.

This paper reports a study on the surface reconstruction on Cu(111) induced by a hyperthermal oxygen molecular beam (HOMB) at room temperature (RT). HOMB incidence at translational energies (E i ) g 0.5 eV induced surface reconstruction to the | -1 3 2 2 | structure for an O coverage (Θ) g 0.27 monolayer (ML). On the other hand, long-range-ordered structures were not formed even at Θ ≈ 0.4 ML for the backfilling of thermal O 2 at RT. No surface reconstruction was induced at E i e 0.23 eV where the attainable Θ value was 0.27 ML for the O 2 exposures below 10 18 molecules/cm 2 . Translational energy above 0.5 eV is required for the dissociative adsorption of O 2 and the resulting surface reconstruction at Θ g 0.27 ML. The O-1s XPS peak for HOMB incidence at RT was resolved into two components, 529.4 and 528.9 eV, at Θ g 0.27 ML, which can be assigned to the O atoms occupying the three-fold hollow sites on unreconstructed Cu(111) and four-coordinated sites on the | -1 3 2 2 | structure, respectively. Annealing the | -1 3 2 2 | reconstructed surface at 620 K decreased Θ to ∼0.27 ML and induced (√13R46.1°× 7R21.8°), the so-called "29" superstructure.

Articles you may be interested in 1,2-Dibromoethane on Cu(100): Bonding structure and transformation to C2H4Kinetics of the CO oxidation reaction on Pt(111) studied by in situ high-resolution x-ray photoelectron spectroscopyThe oxidation processes of Cu͑111͒ with a hyperthermal O 2 molecular beam ͑HOMB͒ were studied using high-resolution x-ray photoemission spectroscopy in conjunction with a synchrotron radiation source. The O-uptake curves were precisely measured at ϳ300 K when irradiating with 2.3 and 0.6 eV HOMB on a Cu͑111͒ surface. A Langmuir-type adsorption model at an oxygen coverage ͑⌰͒р0.4 ML describes the kinetics of dissociative adsorption in the HOMB incidence. On the other hand, further inefficient oxidation occurs even for the 2.3 eV HOMB irradiation at ⌰у0.4 ML. A collision-induced absorption mechanism can interpret the slow oxidation process of Cu͑111͒.

Oxidation of Cu3Au(100) using a hyperthermal O2 molecular beam (HOMB) was investigated by x-ray photoemission spectroscopy in conjunction with a synchrotron light source. From the incident energy dependence of the O-uptake curve, it was determined that the dissociative adsorption of O2 implies a higher activation barrier and therefore less reactivity compared to Cu, owing to the Au alloying. The dissociative adsorption progresses with the Cu segregation on the surface. No prominent growth of Cu2O even for 2eV HOMB suggests that the Au alloying of Cu can serve as a protective layer against further oxidation into the bulk.

We studied the oxidation of Cu(410) using high-resolution electron energy loss spectroscopy and X-ray photoemission spectroscopy performed with synchrotron radiation. Cu2O formation starts above half a monolayer oxygen coverage, and the oxidation rate is larger,than for the parent low Miller index Cu(100) surface. Open steps favor therefore the process by opening pathways for subsurface migration and oxygen incorporation. Oxidation occurs only above 500 K when dosing O-2 by backfilling, but the ignition temperature can be lowered to room temperature by dosing O-2 Via a supersonic molecular beam at hyperthermal energy indicating the opening of a different pathway. The oxidation rate is maximal at normal incidence; at grazing incidence, it is higher when O-2 impinges nearly normal to the (100) nanofacets than when it hits the surface close to the normal to the step rises. A collision induced absorption mechanism can explain the experimental findings

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