Condensed-phase sample

For a gas in laminar flow over a condensed phase sample of length L, the mass transport across the boundary layer, in terms of the flux of molecules from the sample to die gas phase, is therefore... 

For non-volatile sample molecules, other ionisation methods must be used, namely desorption/ionisation (DI) and nebulisation ionisation methods. In DI, the unifying aspect is the rapid addition of energy into a condensed-phase sample, with subsequent generation and release of ions into the mass analyser. In El and Cl, the processes of volatilisation and ionisation are distinct and separable in DI, they are intimately associated. In nebulisation ionisation, such as ESP or TSP, an aerosol spray is used at some stage to separate sample molecules and/or ions from the solvent liquid that carries them into the source of the mass spectrometer. Less volatile but thermally stable compounds can be thermally vaporised in the direct inlet probe (DIP) situated close to the ionising molecular beam. This DIP is standard equipment on most instruments an El spectrum results. Techniques that extend the utility of mass spectrometry to the least volatile and more labile organic molecules include FD, EHD, surface ionisation (SIMS, FAB) and matrix-assisted laser desorption (MALD) as the last... 

In a supersonic jet, the fluorescence spectra are virtually free of environmental perturbations (in contrast to condensed-phase samples) and can thus provide information on isolated solute molecules. Moreover, van der Waals complexes with other solute molecules can be studied, which is of great fundamental interest. 

Gold s method has been used by a number of workers, including Siska (1973), who applied it to molecular-beam scattering data, MacNeil and Dixon (1977), who applied it to photoelectron spectra, and Jones et al. (1967), who restored infrared spectra of condensed-phase samples. The author is unaware of any experimental results with this method, however, that illustrate the full potential achievable by constrained methods to be described later in this chapter. In the work of Jones et al., the resulting resolution is probably limited by the inherent breadth of spectral lines observed with condensed-phase samples. 

Infrared emission spectroscopy can be used for the laboratory study of heated samples as one would encounter in pyrot reactions or in the detonation of primary expls. One difficulty associated with the measurement of emission spectra of condensed phase samples is that the temp of the sample has to be uniform, or else radiation emitted from elements situated below the surface will be absorbed by the cooler particles near the surface. Emission spectrometry finds application in the study of flames and smoke... 

Because of the nonlinearity of CRS, conventional wisdom states that high input field peak amplitudes, which are readily provided by ultrashort laser pulses, are required to induce a strong nonlinear polarization (cf. (6.1)— (6.3)). The use of transform-limited femtosecond pulses, however, results in a broad distribution of Raman shifts, uy, — ujs, that by far exceeds the line width of a typical Raman resonance ( —-10 r-rn ) in condensed-phase samples at room temperatures. This is schematically depicted in Fig. 6.2A where the frequency-time dependences of a transform-limited pump and Stokes... 

From the point of view of theory, the formulae of Table 2.6 are equally applicable to both gas and condensed phase samples, as they include the local field factors, which account for local modifications to the Maxwell fields due to bulk interactions within the Onsager-Lorentz model. 

In summary, we have combined state of the art optical multichannel analyzer techniques with well established low repetition rate picosecond laser technology to construct an instrument capable of measuring transient spectra with unprecedented reliability. It is, in its present form, a powerful tool for the investigation of ultrafast processes in biological, chemical, and physical systems. We foresee straightforward extension of the technique to the use of fourth harmonic excitation (at 265 nm) and also a future capability to study gaseous as well as condensed phase samples over a more extended spectral range. 

The condensed-phase samples will be reacted with water to determine the abundance of various lithium compounds. If lithium carbide is present, acetylene will be produced when the lithium carbide is reacted with water. Other compounds (LiH and Li) should release hydrogen when contacted with water, These gases will be measured with a gas chromatograph. 

Condensed-phase samples containing volatile analytes require special techniques because the volatile components are elusive... 

Gillette PC, Lando JB, Koening JL (1985) A survey of infrared spectral data processing techniques In Ferraro JR, Basile LJ (eds) Fourier transform infrared spectroscopy -applications to chemical systems, Vol 4 Academic Press, New York, 1-47 Graham JA, Grim WM III, Fateley WG (1985) Fourier transform infrared photoacoustic spectroscopy of condensed-phase samples, In Ferraro JR, Basile LJ (eds) Fourier transform infrared) spectroscopy - applications to chemical systems, Vol 4 Academic Press, New York, 345-392... 

Measurement procedures using solutions in standard cuvettes are well developed. Some condensed phase samples such as large crystals and polymer films are relatively robust and easily mounted. Two areas of interest which have led to innovation are in the mounting of small, enviromnentally sensitive, single crystals and in the sample cells used for frozen glasses, particularly those having a substantial aqueous phase, such as proteins. 

Graham. J. A., Grim, N. M. and Fately, W. G. (1985). Fourier Transform infrared photoacoustic spectroscopy of condensed-phase samples. In Fouriertransform infrared spectroscopy Vol. 4 (ed. J. R. Ferraro and L. J. Basil), pp. 345-92. Academic Press, New York. [129]... 

Ionization of the analyte is the first crucial and challenging step in the analysis of any class of compounds by mass spectrometry. The key to a successful mass spectrometric experiment lies to a large extent in the approach to converting a neutral compound to a gas-phase ionic species. A wide variety of ionization techniques have become available over the years, but none has universal appeal. In some techniques, ionization is performed by ejection or capture of an electron by an analyte to produce a radical cation [M+ ] or anion [M ], respectively. In others, a proton is added or subtracted to yield [M - - H]+ or [M — H] ions, respectively. The adduction with alkali metal cations (e.g., Na+ and K+) and anions (e.g., Cl ) is also observed in some methods. The choice of a particular method is dictated largely by the nature of the sample under investigation and the type of information desired. Table 2.1 lists some of the methods currently in vogue. Some methods are applicable to the atomic species, whereas others are suitable for molecular species. Also, some methods require sample molecules to be present in the ion source as gas-phase species, whereas others can accommodate condensed-phase samples. The methods that are applicable to molecular species are the subject of the present chapter those applicable to atomic species are described in Chapter 7. 

---