Resolution, of ion

Femtosecond photoion (photoelectron) microscopy combines the merits of two types of microscopy the high spatial resolution of ion projective microscopy and the high spectral (energy) resolution of optical spectroscopy. From this point of view, photoion microscopy is an interesting example of wave-corpuscular microscopy. Indeed, there are two well-known types of microscopy wave (optical) and corpuscular (electron, ion). 

Rollag JG, Nachi R, Schlesiger L, et al. The resolution of ion suppression caused by drug-interaction compounds. (2001) ASMS Conference Proceedings. 

When an ion swarm is injected into the drift region of the drift tube, spatial resolution of ions of differing mobility can be separated as differences in drift velocity as the ions move toward the detector, here at virtual ground. Separate packets or swarms of ions develop with the separation as shown in Fig. 2, where three ion swarms have been resolved in time and space. As ions collide with the detector, commonly a simple metal disc or Faraday plate, neutralization of ions is accompanied by electron flow in the detector plate this is amplified and shown in the inset of Fig. 2. Thisplot of detector response(current or voltage) versus time (in ms) is called a mobility spectrum and is the... 

LL Haney, DE Riederer. Delayed extraction for improved resolution of ion/surface collision products by time-of-flight mass spectrometry. Anal Chim Acta 397 225-233,1999. 

In the EOID detector of I igure I l-4a, a phosphorescent. screen is placed behind the microchannel plale so that the cascade of electrons produces a flash of light that is directed to an optical array detector via fiber optics. The data collected from the array detector then provide two-dimensional resolution of ions appearing al the focal plane of a mass spcclronicler. 

Buryakov, I.A., Ion current amplitude and resolution of ion mobility increment spectrometer (IMIS). Int. J. Ion Mobility Spectrom. 2001, 4, 112. 

Figure 8.9 (a) MALDI mass spectrum of poly(ethylene glycol) 20000 using HABA as matrix with sodium cationization and time-lag focusing set to optimize the resolution of ions at m/z 23000. (b) Expansion of (a) in the high mass region of the spectrum, (c) Expanded MALDI mass... 

RESOLNRA A new program for optimizing the achievable depth resolution of ion beam analysis methods Mayer, M. (2008) Nud. Instrum. Methods Phys. Res., Sect. B, 266 (8), 1852. 

In the simplest fomi, reflects the time of flight of the ions from the ion source to the detector. This time is proportional to the square root of the mass, i.e., as the masses of the ions increase, they become closer together in flight time. This is a limiting parameter when considering the mass resolution of the TOP instrument. 

The final velocity of these two ions will be the same, but their final flight times will differ by the above turnaround time, This results in a broadening of the TOF distributions for each ion mass, and is anotiier limiting factor when considering the mass (time) resolution of the instrument. 

Molecular beam sample introduction (described in section (Bl.7.2)). followed by the orthogonal extraction of ions, results in improved resolution in TOP instruments over eflfrisive sources. The particles in the molecular beam typically have translational temperatures orthogonal to the beam path of only a few Kelvin. Thus, there is less concern with both the initial velocity of the ions once they are generated and with where in the ion source they are fonned (since the particles are originally confined to the beam path). 

This method relies on the simple principle that the flow of ions into an electrolyte-filled micropipette as it nears a surface is dependent on the distance between the sample and the mouth of the pipette [211] (figure B 1.19.40). The probe height can then be used to maintain a constant current flow (of ions) into the micropipette, and the technique fiinctions as a non-contact imaging method. Alternatively, the height can be held constant and the measured ion current used to generate the image. This latter approach has, for example, been used to probe ion flows tlirough chaimels in membranes. The lateral resolution obtainable by this method depends on the diameter of the micropipette. Values of 200 nm have been reported. 

The ability to identify different mass species depends on the energy resolution of the detector which is typically 15 keV fiill width at half maximum (FWFIM). For example, silver has a mass M2 = 108 and tin has a mass A , = 119. The difference between . = 0.862 and = 0.874 is 0.012. For 2 MeV helium ions the... 

Smith, R. L. Popham, R. E. The Quantitative Resolution of a Mixture of Group II Metal Ions by Thermometric Titration with EDTA, /. Chem. Educ. 1983, 60, 1076-1077. 

In general terms, the main function of the magnetic/electric-sector section of the hybrid is to be able to resolve m/z values differing by only a few parts per million. Such accuracy allows highly accurate measurement of m/z values and therefore affords excellent elemental compositions of ions if these are molecular ions, the resulting compositions are in fact molecular formulae, which is the usual MS mode. Apart from accurate mass measurement, full mass spectra can also be obtained. The high-resolution separation of ions also allows ions having only small mass differences to be carefully selected for MS/MS studies. 

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