نتایج جستجو برای: laser ionization
تعداد نتایج: 207613 فیلتر نتایج به سال:
Laser desorption/ionization from structured surfaces has been the object of recently renewed interest. Conditions in the plume of material ablated from such surfaces may differ from those of a sample which is ablated in bulk. Since recombination and secondary ion-molecule reactions in the plume play a major role in determining the types and quantities of ions observed at the detector, these dif...
BACKGROUND Most published literature using SELDI-TOF has used traditional techniques in Spectral Analysis such as Fourier transforms and wavelets for denoising. Most of these publications also compare spectra using their most prominent feature, i.e, peaks or local maximums. METHODS The maximum intensity value within each window of differentiable m/z values was used to represent the intensity ...
Isotope selective effects in resonance ionization mass spectrometry (RIMS) pose a potentially serious limitation to the application of this technique to the precise and reproducible measurement of isotope ratios. In order to identify some of the underlying causes of isotope selectivity in RIMS and to establish procedures for minimizing these effects, we investigated laser-induced isotope select...
Laser ablation involves heating, evaporation of target material and ionization of vapor to form plasma plume surrounding the ablation spot. A self consistent model, that combines target heating, evaporation, ionization, shielding and expansion of plume, is employed to obtain ablation parameters. The results showed good agreement with experiments. For a given laser energy fluence and target mate...
We present ionization probability and line shape calculations for the two-step 3-photon ionization process, 1S 2~ω −→ 2S ~ω −→ εP , of the ground state of hydrogenic atoms in a non-monochromatic laser field with a time–dependent amplitude. Within the framework of a three–level model, the AC Stark shifts and non-zero ionization rates of all states involved were taken into account together with s...
Electron motion in chemical bonds occurs on an attosecond timescale. This ultrafast motion can be driven by strong laser fields. Ultrashort asymmetric laser pulses are known to direct electrons to a certain direction. But do symmetric laser pulses destroy symmetry in breaking chemical bonds? Here we answer this question in the affirmative by employing a two-particle coincidence technique to inv...
Modified Si wafers and nanoparticles (5-50 nm) have been developed and explored to assist laser desorption ionization mass spectrometry (LDI-MS) for small molecule analysis. DIOS (desorption/ionization on silicon) plates were prepared according to published protocols. DIOS was tested and compared with the optimized silicon nanoparticles derivatized by penterfluorophenylchlorosilane (PFP). SPALD...
Ambient analysis of metabolites and lipids from unprocessed animal tissue by mass spectrometry remains a challenge. The utility of the two novel ambient ionization techniques--atmospheric pressure infrared matrix-assisted laser desorption ionization (AP IR-MALDI) and laser ablation electrospray ionization (LAESI)--is demonstrated for the direct mass spectrometric analysis of lipids and other me...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید