Mode source region

The column effluent from the LC is nebulized into the atmospheric-pressure ion source region. Typical solvents used are mixtures of water and methanol or acetonitrile, containing up to lOmmoll electrolyte, such as formic acid or ammonium acetate. Nebulization can be performed either by means of a strong electrical field, or by a combination of the strong electric field and pneumatic nebulization. The latter is sometimes named pneumatically assisted electrospray or ionspray . The pure electrospray process is limited to flow rates up to 10 pi min Pneumatically assisted electrospray enables the introduction of higher flow rates, up to Imlmin. Since ion production mechanisms between the two modes are identical, the term electrospray is used here throughout. 

Fignre 14.6. ES mass spectra of apomyoglobin obtained by Q3 scan on a triple quadnqmle with Q1 set at miz 2000 in if-only mode (low mass cutoff < 1633) declustering in the ion source region was negligible, (a) No CID gas in Q2 (b) CID gas was added to Q2. (Reprinted from Ref. 79 with permission.)... 

In this mode, ions are formed continuously in the ion source (a), but the electrostatic accelerating potential is applied in pulses (b). Thus, a sample of ions is drawn into the drift region (c) with more ions formed in the source. As shown in Figure 26.1, the ions separate according to m/z values (d) and arrive at the detector (e), the ions of largest m/z arriving last. 

The Ti02 (001) surface was cleaned and reduced by cycles of ion bombardment as previously described [3]. The distribution of titanium oxidation states was determined from cxirve fitting the Ti(2p3/2) envelope in x-ray photoelectron spectra [3]. After surface preparation, reaction experiments were conducted in either the TPD or steady state mode. TPD experiments have been described [1]. XPS spectra were also obtained following a saturation exposure of the sample using the same procedure as that for the TPD experiments. After pump down, the crystal was placed under the Mg X-ray source and the Ti(2p), 0(ls), and C(ls) regions were scanned. For steady-state experiments a dosing needle was aligned perpendicular to the axis of the mass spectrometer. It was used to direct a steady beam of methylacetylene (Linde, 95%) at the crystal surface when the sample was placed at the aperture of the mass spectrometer. Steady state reaction experiments were... 

In situ XRD spectra were collected on beam line X18A at the National Synchrotron Light Source (NSLS) located at Brookhaven National Laboratory (BNL). The X-ray wavelength (X) was 1.195 A. The step size of the 29 scan was 0.02° in the regions with Bragg reflections and 0.05° in the regions without reflections. The XRD spectra were collected in the transmission mode (Liu et al., 2004). 

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