Evaluation of different sample introduction approaches for the determination of boron in unalloyed steels by inductively coupled plasma mass spectrometry

An extended study of different sampling introduction approaches using inductively coupled plasma mass spectrometry (ICP-MS) is presented for the determination of boron in steel samples. The following systems for sample introduction were applied: direct sample solution nebulization by continuous nebulization (CN) using a cross-flow nebulizer and with flow injection (FI), applied to 0.1% (m/v) and 0.5% (m/v) sample solutions, respectively; FI after iron matrix extraction, using acetylacetone–chloroform, and isotopic dilution (ID) analysis as the calibration method; FI with on-line electrolytic matrix separation; and spark ablation (SA) and laser ablation (LA) as solid sampling techniques. External calibration with matrix-matching samples was used with CN, SA, and LA, and only acid solutions (without matrix matching) with FI methods. When FI was directly applied to a sample solution, the detection limit was of 0.15 μg g⁻¹, improving by a factor of 4 that was obtained from the CN measurements. Isotopic dilution analysis, after matrix removal by solvent extraction, made it possible to analyse boron with a detection limit of 0.02 μg g⁻¹ and, with the on-line electrolytic process, the detection limit was of 0.05 μg g⁻¹. The precision for concentrations above 10 times the detection limit was better than 2% for CN, as well as for FI methods. Spark and laser ablation sampling systems, avoiding digestion and sample preparation procedures, provided detection limits at the μg g⁻¹ levels, with RSD values better than 6% in both cases. Certified Reference Materials with B contents in the range 0.5–118 μg g⁻¹ were used for validation, finding a good agreement between certified and calculated values.     

Plasma chemistry in laser ablation processes

Based on the results of quantitative spectroscopic diagnostics (LIF in combination with time resolved emission spectroscopy) chemical dynamics in laser-produced plasmas of metallic (Ti, Al,), and graphite samples have been examined. The Nd-YAG (1064 nm, 10 ns, 100 mJ) and excimer XeCl (308 nm, 10 ns, 10 mJ) lasers were employed for ablation. The main attention was focused on the elucidation of a role of oxide and dimer formation in controlling spatio-temporal distributions of different species in the ablation plume. The results of the spatial and temporal analysis of a laser-produced plasma in air indicates the existence of diatomic oxides in the ablation plume both in the ground and excited states, which are formed from reactions between ablated metal atoms and oxygen. The efficiency of the oxidation reaction depends on the intensity and spot diameter of the ablation laser beam. The maximal concentration of TiO molecules are estimated to be of 1×10¹⁴ cm⁻³ at the time of 10 μs after the start of the ablation pulse. A comparison of spatial–temporal distributions of Ti atoms and excited TiO molecules allow us to find a correlation in their change, which proves that electronically excited Ti oxides are most probably formed from oxidation of atoms in the ground and low lying metastable states. The spectroscopic characterization of pulsed laser ablation carbon plasma has also been performed. The time–space distributions as well as the high vibrational temperature of C₂ molecules indicate that the dominant mechanism for production of C₂ is the atomic carbon recombination.     

Binder-free carbon-coated nanocotton transition metal oxides integrated anodes by laser surface ablation for lithium-ion batteries

In this paper, an efficient laser surface ablation strategy for producing binder-free carbon-coated nanocotton CoO-Co integrated anode is reported. The fabrication process introduces in-situ growing nanocotton-like CoO on the surface of Co foil via ablating with a nanosecond laser. After that, coated with dopamine as carbon source, the CoO-Co composite foil is heated in Argon atmosphere to form a CoO@C-Co foil as an anode of LIB. The laser surface ablation exhibits high fabrication speed (~10 minutes) and significantly reduces the processing time. The obtained binder-free CoO@C-Co integrated anode shows a unique cotton-like villous structure with large specific surface area and an active material/current collector integrated architecture, which provides a stabilized rapid electronic conduction path. When tested as an anode for LIBs, the CoO@C-Co integrated anode possesses superior performance: First discharge capacity of 1301.5 mAh g⁻¹ is achieved at a current density of 0.1 A g⁻¹. Also at a high current density of 1.5 A g⁻¹, the second discharge capacity of 791.7 mAh g⁻¹ is achieved. After 800 cycles, reversible capacities of 799.8 mAh g⁻¹ can still be achieved with an average coulombic efficiency of nearly 100%. In addition, this strategy is suitable for the production of other carbon coated transition metal oxides integrated anodes, such as NiO@C-Ni, Fe₂O₃/Fe₃O₄@C-Fe, and CuO/Cu₂O@C-Cu integrated anodes.     

Quasi ‘non-destructive’ laser ablation-inductively coupled plasma-mass spectrometry fingerprinting of sapphires

A homogenized 193 nm excimer laser with a flat-top beam profile was used to study the capabilities of LA-ICP-MS for ‘quasi’ non-destructive fingerprinting and sourcing of sapphires from different locations. Sapphires contain 97–99% of Al₂O₃ (corundum), with the remainder composed of several trace elements, which can be used to distinguish the origin of these gemstones. The ablation behavior of sapphires, as well as the minimum quantity of sample removal that is required to determine these trace elements, was investigated. The optimum ablation conditions were a fluency of 6 J cm⁻², a crater diameter of 120 μm, and a laser repetition rate of 10 Hz. The optimum time for the ablation was determined to be 2 s, equivalent to 20 laser pulses. The mean sample removal was 60 nm per pulse (approx. 3 ng per pulse). This allowed satisfactory trace element determination, and was found to cause the minimum amount of damage, while allowing for the fingerprinting of sapphires. More than 40 isotopes were measured using different spatial resolutions (20–120 μm) and eight elements were reproducibly detected in 25 sapphire samples from five different locations. The reproducibility of the trace element distribution is limited by the heterogeneity of the sample. The mean of five or more replicate analyses per sample was used. Calibration was carried out using NIST 612 glass reference material as external standard. The linear dynamic range of the ICP-MS (nine orders of magnitude) allowed the use of Al, the major element in sapphire, as an internal standard. The limits of detection for most of the light elements were in the μg g⁻¹ range and were better for heavier elements (mass >85), being in the 0.1 μg g⁻¹ range. The accuracy of the determinations was demonstrated by comparison with XRF analyses of the same set of samples. Using the quantitative analyses obtained using LA-ICP-MS, natural sapphires from five different origins were statistically classified using ternary plots and principal multi-component analysis.     

Can Humans Metabolize Arsenic Compounds to Arsenobetaine?

Arsenic compounds were determined in 21 urine samples collected from a male volunteer. The volunteer was exposed to arsenic through either consumption of codfish or inhalation of small amounts of (CH₃)₃As present in the laboratory air. The arsenic compounds in the urine were separated and quantified with an HPLC–ICP–MS system equipped with a hydraulic high-pressure nebulizer. This method has a determination limit of 0.5 μg As dm⁻³ urine. To eliminate the influence of the density of the urine, creatinine was determined and all concentrations of arsenic compounds were expressed in μg As g⁻¹ creatinine. The concentrations of arsenite, arsenate and methylarsonic acid in the urine were not influenced by the consumption of seafood. Exposure to trimethylarsine doubled the concentration of arsenate and increased the concentration of methylarsonic acid drastically (0.5 to 5 μg As g⁻¹ creatinine). The concentration of dimethylarsinic acid was elevated after the first consumption of fish (2.8 to 4.3 μg As g⁻¹ creatinine), after the second consumption of fish (4.9 to 26.5 μg As g⁻¹ creatinine) and after exposure to trimethyl- arsine (2.9 to 9.6 μg As g⁻¹ creatinine). As expected, the concentration of arsenobetaine in the urine increased 30- to 50-fold after the first consumption of codfish. Surprisingly, the concentration of arsenobetaine also increased after exposure to trimethylarsine, from a background of approximately 1 μg As g⁻¹ creatinine up to 33.1 μg As g⁻¹ creatinine. Arsenobetaine was detected in all the urine samples investigated. The arsenobetaine in the urine not ascribable to consumed seafood could come from food items of terrestrial origin that—unknown to us—contain arsenobetaine. The possibility that the human body is capable of metabolizing trimethyl- arsine to arsenobetaine must be considered. © 1997 by John Wiley & Sons, Ltd.     

Line broadening mechanisms in the low pressure laser-induced plasma

The spectral profiles of Ca and Rb lines have been studied in a laser induced plasma as a function of pressure (1–10 torr) and delay time with respect to the plasma initiation (1–10 μs). Measurements were made in a plasma induced by the 1064-nm output of a Nd:YAG laser on a calcium carbonate matrix, doped with Rb. Spectral profiles were measured in absorption using a narrow-band cw Ti:Sapphire laser. It was shown that in the case of a trace element (Rb in a CaCO₃ matrix), the broadening mechanism was Doppler-dominant, whereas for a major matrix component (Ca), resonance broadening was the main contributor to the line shape. The plasma was shown to be non-equilibrium provided by the difference between the kinetic (3000 K) and the excitation (8000 K) temperatures. The electron number density at delay times of 5–10 μs and pressures of 1–10 torr was estimated not to exceed 10¹⁵ cm⁻³. The number densities of Ca atoms in the ground and the excited (23 652 cm⁻¹) states were evaluated by measuring line width and peak absorption at 732.6 nm. They were found to be in the range of (1.5–2.2)×10¹⁷ cm⁻³ for the ground state and (1.5–33)×10¹¹ cm⁻³ for the excited state.     

Optical emission spectroscopy and modeling of plasma produced by laser ablation of titanium oxides

In the present study, the time evolution of electron number density, of electron, atom and ion temperatures, of plasma produced by KrF excimer laser ablation of titanium dioxide and monoxide targets, are investigated by temporally and spatially resolved optical emission spectroscopy over a wide range of laser fluence from 1.7 to 6 J cm⁻², oxygen pressures of 10⁻²–10⁻¹ torr and in a vacuum. A state-to-state collisional radiative model is proposed for the first time to interpret the experimental results at a distance of 0.6 mm from the target surface, in vacuum and for a time delay from 100 to 300 ns from the beginning of the laser pulse. In particular, we concentrate our attention on problems concerning the existence of the local thermodynamic conditions in the laser-induced plasma and deviation from them, as observed in our experiment. The numerical model proposed for calculating the electron number density and the population densities of atoms and ions in excited states give good quantitative agreement with the experimental results of the optical emission spectroscopy measurements.     

Element selective detection of chlorine in capillary gas chromatography by wavelength modulation diode laser atomic absorption spectrometry in a microwave induced plasma

A new element selective detector for gas chromatography is presented. The detector, based on wavelength modulation diode laser atomic absorption spectrometry in a microwave induced helium plasma, is used for measurements of chlorinated hydrocarbons by absorption of excited, metastable chlorine atoms. Indications of complete dissociation of the halocarbons in the plasma have been found. Preliminary detection limits of the order of 1 μg ml⁻¹ or 80 pg s⁻¹ have been found for different halocarbons.     

Photochemistry on surfaces: Fluorescence emission of monomers and dimers and triplet state absorption of acridine orange adsorbed on microcrystalline cellulose

Prompt fluorescence as well as delayed fluorescence emission of acridine orange was detected at room temperature from samples where this dye is adsorbed on microcrystalline cellulose. Ground state absorption studies provided evidence for dimer formation of the dye when adsorbed on cellulose, and the equilibrium constant for dimerisation was determined as 1.6±0.1 × 10⁶mol⁻¹g. At low loadings of acridine orange on cellulose (<1 μmol g⁻¹) the fluorescence emission is mainly due to the monomer and is similar to that observed in ethanolic solutions where little aggregation occurs, and peaks at 530 nm. A linear dependence of the fluorescence intensity on the amount of light absorbed by the dye was established for these “diluted” samples. However, at higher loadings (>20 μmol g⁻¹), the fluorescence intensity decreases, and the emission is broad with its maximum at 620 nm, and is mainly due to the dimer. By assuming that the excited monomer and dimer of acridine orange are the only emitting species, it was possible to determine the fluorescence quantum yields for these two species when adsorbed on microcrystalline cellulose as 0.95±0.05 and 0.40±0.10, respectively. Pulsed emission studies at room temperature in the millisecond time-range also revealed monomer and dimer emissions on this longer time-scale. These are shown to be due to thermally activated delayed fluorescence arising from the triplet states of monomer and dimer acridine orange as confirmed by diffuse reflectance transient absorption studies.     

Intermolecular vibrations and dynamics of the anisole—benzene complex studied by multi-resonance spectroscopy

The intermolecular vibrations of the anisole—benzene complex in the ground and excited electronic states have been observed by the LIF (laser-induced fluorescence) and fluorescence-dip techniques. Short progressions due to the intermolecular vibrations suggest a small structure change of the complex upon electronic excitation. The LIF excitation spectrum shows predominant progressions of 27 cm⁻¹, which is tentatively assigned to one of the intermolecular bending modes in the excited electronic state. On the other hand, the fluorescence-dip spectrum shows only a series of bands with irregular intervals due to the intermolecular modes in the ground electronic state. The decay rates of the vibrationally excited complex in the ground electronic state have also been measured with the SEP-LIF (stimulated emission pumping-laser-induced fluorescence) technique, where the complex vibrationally excited by SEP is probed by the delayed LIF measurements. The complex excited to its purely intermolecular mode stays in the initially prepared state after a delay time of 1 μs. On the other hand, the complex excited to the intramolecular vibrational states above 500 cm⁻¹ does not seem to stay in the prepared states. Neither the relaxed complex nor the dissociated monomer was detected. A possible reason for this observation is discussed.     

Inductively coupled plasma-atomic emission spectrometry method for determination of trace metals in alkaline-earth matrices after flotation separation

An inductively coupled plasma-atomic emission spectrometry (ICP-AES) method is developed for determination of Cd, Co, Cr, Cu, Ni, Tl and Zn in traces in calcite, CaCO₃, dolomite, CaMg(CO₃)₂, and gypsum, CaSO₄. Interferences of a Ca/Mg matrix on analyte intensities were investigated. The results reveal that Ca does not interfere with Cr, Ni and Zn, but tends to decrease the intensity of the other elements. Magnesium as a matrix element does not interfere on with Zn, but increases the intensities of Ni, Cr and Cu, and decreases the intensities of Cd, Co and Tl. To eliminate these matrix interferences on trace element intensities, a flotation separation method is proposed. Lead(II) hexamethylenedithiocarbamate, Pb(HMDTC)₂, is applied as a collector for flotation of trace elements from acidic solutions of mineral samples. The flotation of acidic aqueous solutions of calcite, dolomite and gypsum was performed at pH 6.0, using 10 mg l⁻¹ Pb and 0.3 mmol l⁻¹ HMDTC⁻ added to 1 l of solution tested. The method detection limits of analytes in different minerals range from 0.02 to 0.06 μg g⁻¹ for Cd, 0.04 to 0.10 μg g⁻¹ for Co, 0.03 to 0.13 μg g⁻¹ for Cr, 0.02 to 0.16 μg g⁻¹ for Cu, 0.09 to 0.30 μg g⁻¹ for Ni, 6.45 to 7.71 μg g⁻¹ for Tl and 0.18 to 0.20 μg g⁻¹ for Zn.     

Laser ablation–inductively coupled plasma–dynamic reaction cell–mass spectrometry for the multi-element analysis of polymers

In this work, the potential of laser ablation–inductively coupled plasma–mass spectrometry for the fast analysis of polymers has been explored. Different real-life samples (polyethylene shopping bags, an acrylonitrile butadiene styrene material and various plastic bricks) as well as several reference materials (VDA 001 to 004, Cd in polyethylene) have been selected for the study. Two polyethylene reference materials (ERM-EC 680 and 681), for which a reference or indicative value for the most relevant metals is available, have proved their suitability as standards for calibration.Special attention has been paid to the difficulties expected for the determination of Cr at the μg g^− 1 level in this kind of materials, due to the interference of ArC⁺ ions on the most abundant isotopes of Cr. The use of ammonia as a reaction gas in a dynamic reaction cell is shown to alleviate this problem, resulting in a limit of detection of 0.15 μg g^− 1 for this element, while limiting only modestly the possibilities of the technique for simultaneous multi-element analysis. In this regard, As is the analyte most seriously affected by the use of ammonia, and its determination has to be carried out in vented mode, at the expense of measuring time.In all cases studied, accurate results could be obtained for elements ranging in content from the sub-μg g^− 1 level to tens of thousands of μg g^− 1. However, the use of an element of known concentration as internal standard may be needed for materials with a matrix significantly different from that of the standard (polyethylene in this work).Precision ranged between 5% and 10% RSD for elements found at the 10 μg g^− 1 level or higher, while this value could deteriorate to 20% for analytes found at the sub-μg g^− 1 level. Overall, the technique evaluated presents many advantages for the fast and accurate multi-element analysis of these materials, avoiding laborious digestion procedures and minimizing the risk of analyte losses due to the formation of volatile compounds.     

Rate constants of the near-resonant E-E energy exchange processes SeS(b0+) + O2(X3Σg−) ⇌ SeS(X10+) + O2(a1Δg)

SeS radicals generated in a fast flow system were excited to their b0⁺, ν' = 0 vibronic state by absorption of Raman-shifted dye laser pulses at 1280 nm. From time-resolved measurements of the b0⁺ → X₁0⁺ fluorescence as a function of added gas pressure, the radiative lifetime of the b0⁺ = 0 state (τ₀ = 400 ± 100 μs) and quenching rate constants for H₂, D₂, N₂, CO, O₂, and CO₂ were deduced. Quenching of SeS(b0⁺, ν'= 0) by O₂ is attributed to the near-resonant electronic- to-electronic energy-transfer process (1), SeS(b0⁺, ν'₁ = 0) + O₂(X³Σ_g⁻, ν″₁ = 0) ⇌ SeS(X₁0⁺, ν″_f = 0) + O₂(a¹Δ_g, ν'_f = 0)−77 cm⁻¹, for which (k₁ = (1.4±0.3) × 10⁻¹² cm³ s⁻¹ was obtained. On the assumption of detailed balancing, k₋₁ was calculated to be (3.0 ± 0.7) × 10⁻¹²cm³ s⁻¹.     

Measurements of rubidium in standard reference samples by wavelength-modulation diode laser absorption spectrometry in a graphite furnace

An investigation of the capabilities of the WM-LDAS-GF (wavelength-modulation laser diode absorption spectrometry in graphite furnaces) technique for detection of Rb at low pg ml⁻¹ concentrations in samples with complex matrices has been performed. Five reference materials were investigated with respect to their Rb content by the WM-LDAS-GF technique: corn bran (NIST 8433); NIST water; (1643d) riverine water (SLRS-2); estuarine water (SLEW-1); and sea water (NASS-3). Freeze-dried corn bran was found to have a Rb concentration of 440 ± 70 ng g⁻¹. This compares well with the certified concentration of 500 ± 300 ng g⁻¹. The Rb content of the NIST water was assessed to 12.7 ± 1.7 ng ml⁻¹. This compares excellently with the specified (although not certified) level of 13 ng ml⁻¹. None of the three other reference materials has any certified Rb level. The Rb content of riverine water was found to be 3.4 ± 0.8 ng ml⁻¹. Chemical interferences were encountered when estuarine water and sea water were analyzed (loss of Rb as RbCl). Addition of NH₄NO₃ as the matrix modifier increased the Rb recovery values considerably (although not fully to unity). Estuarine water and sea water were found to have Rb contents of 30 ± 10 ng ml⁻¹ and 140 ± 50 ng ml⁻¹, respectively. A detection limit for Rb in deionized water of 10 fg (corresponding to a concentration of 1 pg ml⁻¹ using a 10 μL aliquot) was obtained. This is identical to (and thus verifies) the previously published result by the group of K. Niemax. These results show that the WM-LDAS-GF technique is capable of detecting traces of Rb in samples also with complex matrices.     

Ultrasensitive determination of gold in geogas by laser excited atomic fluorescence spectrometry

Ultratrace gold (Au) in geogas samples has been determined by means of laser excited atomic fluorescence spectrometry combined with graphite electrothermal atomization and time-gate technique. Gold atoms were excited from the ground state to the 6p²P_3/2 state by a pulsed laser beam with a wavelength of 242.8 nm. Fluorescence photons with a wavelength of 312.3 nm were measured by a photon-counting unit. The time-gate technique was used to reduce the background radiation caused by the furnace. This method has proved to be highly sensitive with minimal background interference. Eighty-two geogas samples were analysed and the Au contents obtained were in the range of 0.002–0.182 ng l⁻¹. The study of Au concentration of geogas in soil is of great interest in prospecting gold deposits.     

Long-lived Triplet Excited State of Perylenemonoimide (PMI) in a Diimine Pt(II) Bis-acetylide Complex: Preparation and Study of the Photophysical Property with Transient Spectra

We prepared a N^N Pt(II) bisacetylide complex that has strong absorption of visible light (molar absorption coefficients ϵ=6.7×10⁴ M⁻¹ cm⁻¹ at 570 nm), and the singlet oxygen quantum yield (Φ_Δ) is up to 78 %. Femtosecond transient absorption spectra show the intersystem crossing (ISC) of the complex takes 81.8 ps, nanosecond transient absorption spectra show the triplet excited state lifetime is 7.6 μs. Density functional theory (DFT) computation demonstrated that the S₁ and T₁ states are mainly localized on the perylenemonoimide (PMI) ligands, although the involvement of the Pt(II) centre is noticeable. The complex was used as triplet photosensitizer to generate delayed fluorescence with perylenebisimide (PBI) as the triplet state energy acceptor and emitter, via the intermolecular triplet-triplet energy transfer (TTET) and triplet-triplet annihilation (TTA), the delayed fluorescence lifetime is up to 52.5 μs under the experimental conditions.     

Assessment and application of diode laser induced fluorescence spectrometry in an inductively coupled plasma to the determination of lithium

A diode laser based system for the detection of Li in an inductively coupled plasma (ICP) by diode laser induced fluorescence (DLIF-ICP) has been developed and successfully applied to the determination of lithium in several mineral waters and a thermal salt. The experimental setup is based on an unmodulated, continuous wave diode laser, emitting light at around 670 nm and exciting neutral Li atoms on their 2s ²S–2p ²P° transition, which was coupled to a commercial ICP atomic emission spectrometer. The spectrometer's monochromator, photomultiplier detector and built-in data acquisition software were utilized to collect background corrected fluorescence and emission signals. A simple, three-step measurement procedure was devised that corrected for the contribution of lithium thermal emission and scattered laser light in the analytical signals. Despite the facts that lithium was detected on its neutral atom, which accounts for less than 1% of the total concentration of Li in the ICP, and that only about 1–2% of all atoms could be excited by the laser light at any given time, the limit of detection (LOD) was still found to be as good as 8 μg/L. The LODs of the DLIF-ICP technique are therefore expected to be in the low ng/L range for elements that can be detected under more advantageous conditions. The linear dynamic range was found to be around three orders of magnitude.     

Lifetime measurements on single vibrational levels of C2(d 3Πg) by laser fluorescence excitation

The radiative lifetimes of the six lowest vibrational levels of C₂(d ³Π_g) were obtained from decay time studies of the C₂(d ³Π_g → a ³Π_u) Swan band fluorescence excited by a pulsed tunable dye laser. The lifetime was found to be 120 ± 10 ns, independent of the vibrational level. From the experimental results the dependence of the electronic transition moment on the internuclear distance was derived.     

Strong-Base-Assisted Synthesis of a Crystalline Covalent Triazine Framework with High Hydrophilicity via Benzylamine Monomer for Photocatalytic Water Splitting

Methods to synthesize crystalline covalent triazine frameworks (CTFs) are limited and little attention has been paid to development of hydrophilic CTFs and photocatalytic overall water splitting. A route to synthesize crystalline and hydrophilic CTF-HUST-A1 with a benzylamine-functionalized monomer is presented. The base reagent used plays an important role in the enhancement of crystallinity and hydrophilicity. CTF-HUST-A1 exhibits good crystallinity, excellent hydrophilicity, and excellent photocatalytic activity in sacrificial photocatalytic hydrogen evolution (hydrogen evolution rate up to 9200 μmol g⁻¹ h⁻¹). Photocatalytic overall water splitting is achieved by depositing dual co-catalysts in CTF-HUST-A1, with H₂ evolution and O₂ evolution rates of 25.4 μmol g⁻¹ h⁻¹ and 12.9 μmol g⁻¹ h⁻¹ in pure water without using sacrificial agent.     

Diagnostic study of laser ablated YBa2Cu3Oy plumes

Post-ablation ionisation in conjunction with a reflectron time-of-flight mass spectrometer has been used to investigate a number of species in the ablation plume from a YBa₂Cu₃O_y target. The experiments were carried out using a Q-switched Nd:YAG laser with typical intensities of ≈ 10⁸ W cm⁻² characteristic of the fluences (1 J cm⁻²) required for the pulsed laser deposition of thin superconducting films. By varying the delay between the ablation and the ionisation laser, the velocity distributions of several of the species from the target have been measured simultaneously. It has been observed that, although some of the atoms and molecules (i.e. Cu, Ba and BaO) have similar velocities, the atoms and oxides of Y (Y and YO) have very different velocities. The yttrium atoms and oxides were observed to be slower than the barium atoms and oxides at both ablation wavelengths examined (355 and 532 nm) and at two different distances from the target surface (2 and 3 mm). It is suggested that Ba, Cu and their oxides are ablated directly from the surface as neutrals, whereas Y and YO form clusters in the ablation plume. These clusters are then fragmented by the post-ionisation laser to produce Y and YO ions.