Plume laser ablation

Pulsed laser deposition (PLD) [1-3] uses high-power laser pulses with an energy density of more than 108 W cm 2 to melt, evaporate, excite, and ionize material from a single target. This laser ablation produces a transient, highly luminous plasma plume that expands rapidly away from the target surface. The ablated material is collected on an appropriately placed substrate surface upon which it condenses and a thin film nucleates and grows. 

Solid samples can be introduced into plasmas by vaporizing them with an electrical spark or with a laser beam. Laser volatilization, often called laser ablation, has become a popular method to introduce samples into inductively coupled plasmas. Here a high-powered laser beam, usually a Nd YAG or excimer laser, is directed onto a portion of the solid sample. The sample is then vaporized by radiative heating. The plume of vapor produced is swept into the plasma by means of a carrier gas. 

For the case of both electrically conducting and electrically non-conducting samples, laser ablation combined with AAS may be useful. In this case AAS measurements can be performed directly at the laser plume. Measurement of the non-element specific absorption will be very important, because of the presence of particles, molecules and radicals as well as due to the emission of continuum radiation. In addition, the absorption measurements should be made in the apprppriate zones. When applying laser ablation for direct solids sampling, the atomic vapor produced can also be led into a flame for AAS work, as has previously been described by Kantor et al. [299] in their early work. 

Entrainment and transport of laser ablated plumes for subsequent... 

Kokai, F. Koga, Y. Heimann, R.B. Magnetic field enhanced growth of carbon clusters in the laser ablation plume of graphite. Appl. Surf. Sci. 1995, 96198, 261-266. 

Here, all three components are interpreted as follows the laser-ablated plume containing C2 H2 expands adiabatically immediately after the ablation. Most of them are first brought into the ionization region without... 

Only signals which can be assigned to direct laser ablation products were analyzed (see Scheme 9), maybe with the exception of mass 76/77, which could be a primary product of laser ablation but also a fragment of the electron impact or of reactions in the ablation plume. The resolution of our experimental setup does not allow us to distinguish between these two masses. 

Whitehouse and Buckingham have recently measured the atomic quadrupole moment of graphite and made a correlation with the moment by simply adding up the quadrupole moments of all the carbon atoms. It is interesting to note that the quadrupole moment of benzene is roughly six times the quadrupole moment of the individual carbon atom. Thus one can postulate that the ions observed in Figure 23 are the result of quadrupole-bound electrons to Cn clusters present in the laser ablation plume. Possible polycyclic structures for the carbon clusters observed in the negative ion spectrum produced by RET are... 

In this paper we demonstrate capabilities of double-pulse laser ablation (DPLA) in liquid environment for fabrication of metallic nanoparticles with a narrow size-distribution. We examined optical properties of the silver colloidal solutions prepared by DPLA in order to reveal the role of the second laser pulse in a size change of the particles produced in the ablation plume. 

Laser ablation (LA) is a powerful tool for mass spectrometric sampling of radionuclides from solids. When sufficiently intense laser light strikes a solid, material is removed from the surface. This material can be in the form of atoms, molecules, ions, electrons, or small particles. Several approaches can be used to analyze the surface for these species. The light that usually also is emitted can be resolved by wavelength to identify atomic or molecular species associated with the sample surface. Depending upon the wavelength of the laser, the atoms and ions in the laser plume can be excited, and the resulting emission can be detected. 

Laser ablation-AAS is also useful for insulating samples, where AA analysis is performed directly in the laser plume. Due to the production of various particles in the measurement zone (solid particles, molecules, radicals) and the resulting background emission, appropriate techniques for the correction of spectral interferences must be used. 

In laser ablation, a solid sample is irradiated with a laser pulse that ablates the point of laser-solid contact to produce a plume of ions and neutrals in the vapor space just above the point of laser-solid contact with the sample surface. If this plume is swept into an ionization source or if reactant ions are electrically focused into the ablated sample plume, product ions are formed. These ions can be electrically focused into an IMS for ion mobility analysis. Direct laser ablation followed by ionization from... 

Fig. 6.95 Laser ablation from surfaces and laser excitation of the plasma plume with fluorescence detection...

Laser ablation has been broadly applied and developed for the synthesis of diverse nanomaterials [21,22], In this approach, an incident laser pulse penetrates into the surface of the material within a certain penetration depth. Electrons are removed from the bulk and the irradiated surface is then heated up and vaporized. At a high enough laser flux, the material is converted to plasma. Consequently, the large pressure difference between the laser produced initial seed plasma and ambient atmosphere causes a rapid expansion of the plasma plume and then it cools down. The plasma species will nucleate and grow into desirable nanostructures, either on a substrate or in a cool Hquid medium [21]. 

Probe electrospray ionization (PESI) and TOF-MS were used for direct profiling of phytochemicals in different parts of a fresh tulip bulb [80], which emphasized the possibility of conducting in-vivo MS analysis of less sensitive biological matrices such as plant tissues. Recently, Pan et al. [81] demonstrated single-probe MS which can conduct metabolomic analysis of individual living cells in real time. The diameter of this probe is < 10 pm which makes the device compatible with eukaryotic cells. Atmospheric pressure ion sources are particularly suitable for analysis of live biological specimens. Cellular metabolism does not need to be quenched before analysis. For instance, in laser ablation electrospray ionization (LAESI)-MS, cells are irradiated by a laser beam in order to extract small amounts of cytosolic components, and to transfer them to the ESI plume [82]. 

Kukreja, L.M., Rohlfing, A., Misra, P, HiUenkamp, E, Dreisewerd, K. (2004) Cluster formation in UV laser ablation plumes of ZnSe and ZnO studied by time-of-flight mass spectrometry. Applied Physics A, 78, 641-644. 

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