Hideyuki Matsuta

Removal of inelastic scattering part from Ti2p XPS spectrum of TiO2 by deconvolution method using O1s as response function

Abstract Ti2p and O1s XPS spectra of a clean surface of single crystal TiO 2 fractured in situ were taken to study the removal of the inelastic scattering part from the Ti2p spectrum. The features of inelastic scattering peaks in EELS were more influenced by surface than O1s XPS. It indicates that O1s XPS is proper as the response function to deconvolute a Ti2p spectrum. FWHM of the non-energy loss peak of Ti2p 3/2 is smaller than that of O1s. When the raw O1s spectrum is used as the response function, the deconvoluted spectrum has negative intensity values in some regions and beat waves. The replacement of the non-energy loss peak of O1s with narrower Gaussian peak takes off the beat waves. Peak separation of the deconvoluted spectrum reveals that it has six peaks. Two of them are main peaks of Ti2p 3/2 and 2p 1/2 . The others are classified into two kinds of satellite peaks, whose energy separation from the main peaks are 3 and 13 eV. Although the latter satellites have been discussed by many authors, the former satellites are first reported here.

Emission Characteristics of a Low-Pressure Laser-Induced Plasma: Selective Excitation of Ionic Emission Lines of Copper

Under reduced pressures, the plasmas produced by irradiation of a Q-switched Nd:YAG laser have favorable features as an excitation source for solid samples in atomic emission spectrometry, such as relatively low fluctuation of the emission intensity and a high signal-to-background ratio. For the analytical application of low-pressure laser-induced plasma spectroscopy (LP-LIPS), the spectra should be examined regarding the type of emission lines and their relative intensities. Further, information on the excitation mechanism in the plasma could be useful in determining optimum operation conditions of the experimental parameters. Spectrum patterns of LP-LIP are principally determined by the type of the filled gas. Especially, particular ionic lines of Cu are selectively excited when Ar or Ne are employed as the filled gas. This feature seems to be due to the (quasi-) resonance charge transfer collisions between a ground state ion of the Ar or Ne gas and a ground state atom of Cu. The plasma plume expanding after the laser irradiation also becomes an excitation source for sample atoms introduced by laser ablation.

Control of d.c. bias current in radio-frequency glow discharge source and its emission characteristics

Abstract A novel technique to control r.f.-powered Grimm-style glow discharge plasmas is described. A new channel of d.c. current driven by the self-bias potential is opened by using a low-pass filter circuit and a load resistor; as the result, a large number of electrons can flow along the d.c. circuit channel including the plasma body from the grounded electrode to the sample electrode. This phenomenon is effective for improvement of the detection sensitivity in the optical emission spectrometry. Atomic emission lines having lower excitation energies are predominantly enhanced by a factor of 10–20. The conduction of the d.c. bias current could promote these excitations.

SERS observation of the adsorption behavior of O2, H2O, and SO2 on silver powder surfaces at nearly real environmental conditions

The interaction of O2, H2O, and SO2 on silver powder prepared from the reduction of AgNO3 by NaBH4 was studied by surface-enhanced Raman scattering (SERS) at room temperature. The presence of H2O of about 103 Pa and O2 of about 104-105 Pa was necessary for observation of SERS peaks of SO32− and SO42−. The superoxide ion O2- was observed under high partial pressure for O2 conditions. SERS peaks of atomic oxygen, superoxide ion O2-, SO32−, and SO42− disappeared on evacuation. SERS peaks of surface species such as Ag2O did not disappear on evacuation.

Background subtraction from transition metal 2p XPS by deconvolution using ligand atom XPS: study on first transition metal cyanide complexes

The primary excitation spectra of the first transition metal series 2p X-ray photoelectron spectra for the metal cyanide ions are obtained by a deconvolution method. As the CN− ions coordinate to the transition metal, N1s spectra are used as a response function for the deconvolution using a Fourier transform method. The obtained spectra have flat zero level backgrounds, whereas the universal curve of the Tougaard method cannot remove the full contribution of energy loss. Among some background subtraction methods, the intensity ratios of 2p32 to 2p12 calculated by the present method are closest to the theoretical photoionization cross section ratios.

SERS and XPS observation of the adsorption behavior of NO and NO2 on a silver powder surface

Abstract The influence of H 2 O on the adsorption behavior of NO or NO 2 on a silver powder surface was studied by SERS and XPS at room temperature. Water vapor was found to be responsible for the adsorption of NO on the silver powder surface. When surface species such as Ag 2 O are present on the surface, some of the NO 2 molecules are adsorbed on the surface species to produce NO - 3 , whereas NO molecules are adsorbed on a different site to produce NO - 2 .

Characteristics of fast electrons from Grimm glow discharge He plasmas as an electron source

In a study of d.c. helium Grimm glow discharges applied with a maximum high voltage of 5 kV, it was found that fast electrons emitted from the cathode surface passed right through the negative glow and the hollow anode. This fast electron current corresponds to approximately 50% of the discharge current at a high voltage of 5 kV and a low helium pressure of 0.43 Torr for an aluminium cathode. The characteristics of the fast electrons under various discharge conditions, i.e. for different cathode materials, discharge voltages and helium pressures, were investigated by measuring the electron-induced X-rays, in order to consider whether the glow discharge plasma could have an application as an electron source. It was found that fast electrons were generated more efficiently under a high voltage while using a low gas pressure in the aluminium cathode. The fast electrons were then used as an electron source for the electron-induced X-ray emission analysis of Fe-Mo binary alloys. This experiment indicated that fast electrons from a Grimm glow discharge plasma are useful as a simple and inexpensive electron source in electron-induced X-ray emission analysis.

Simple correlation between Mn-Kα X-ray emission and Mn 2p X-ray photoelectron spectra for high oxidation number or low-spin manganese compounds

The high-resolution Mn-Kα X-ray emission spectra (XES) and Mn 2p X-ray photoelectron spectra (XPS) for K[MnO4], K3[Mn(CN)5(NO)], K2[MnO4] and K3[Mn(CN)6] were measured. The first and second compounds which have no unpaired electrons, give symmetrical peaks in Mn-Kα1 XES and Mn 2p3/2 XPS spectra. The spectra of the other compounds show asymmetrical lines. When the lines are divided into two Lorenzian (for XES) or Gaussian (for XPS) curves, the energy separation and intensity ratio of the two peaks coincide with each other in both spectroscopies. These results are rationalized by spin-unrestricted DV-Xα molecular-orbital calculations of the anions. The electronic structures of these anions are calculated for their ground state and hole states in 1s and 2p levels. It is concluded that the electronic structures of the compounds in the ground states are conserved in the core hole states. Thus the satellite peaks due to charge transfer are not observed and the peak profiles are governed by the exchange splitting between 2p and valence electrons.

SERS observation of the effects of pressure and water on the adsorbed state of nitrogen dioxide on a silver powder surface

The effects of pressure and water on the adsorbed state of nitrogen dioxide on silver powder produced from an aqueous solution of AgNO3 were studied by SERS. NO2 of 102 Pa was added to the silver powder in the sample chamber and then pressure was raised up to ∼ 105 Pa with dry Ar, N2 or O2. The observed surface species are NO-3 and NO-2 ions under atmospheric pressure. When the total pressure decreases, NO-2 is transformed into NO-3 and NO+. This reaction is reversible with the total pressure variation of dry gases regardless of kind. Once the silver powder adsorbing nitrogen oxides is exposed to moistened gas or air of ∼ 105 Pa, the reversible variation was interrupted, and NO-3 and NO-2 ions are observed on the silver surface.

Effect of plasma gas for spectrometric analysis of tin and zinc using low-pressure laser-induced plasma

Abstract The emission characteristics of tramp elements such as Sn and Zn in low-pressure laser-induced plasma have been examined with reference to change of the surrounding gas (Ar, Ne and He). From the pressure dependence of the intensity of Sn I 326.23-nm, Sn II 335.22-nm, Zn I 213.86-nm and Zn II 210.00-nm emission lines, it was found that Sn and Zn atoms could be excited by the collision between surrounding gas species and ablated atoms with large kinetic energy by laser irradiation. Besides the collisional excitation, resonance charge-transfer collision between Zn atoms and Ne ions proved to be effective in the selective excitation of Zn II 206.42-nm and 210.00-nm emission lines, because the emission intensity of these lines was strongly enhanced in Ne atmosphere, and the sum of the excitation energy of these lines and the ionization potential of Zn is very close to the ground-state energy of Ne ions.