Argon probe molecule

Specific surface area determination is most commonly conducted by positive adsorption studies (Section 7.6.4.2), and here the election of the probe molecule is very important. The most traditional and widely used method is N2 adsorption at 77 K, using the BET isotherm to evaluate monolayer coverage (Section 7.6.4.2) sometimes other inert gases, such as argon, are employed in the same conditions (Sposito 1984). In soil characterization, other substances are also used in the BET... 

In this paper we have proposed definitions for the three main methods of gas adsorption in an attempt to clarify the confusion evident from published literature. We have also shown that, for microporous analysis, careful selection of analysis conditions is necessary to achieve meaningful results. Using commercially available instrumentation, we have demonstrated uniquely detailed isotherms of zeolite materials using both argon and water as probe molecules. Commercial instruments that can measure and record a large number of data points at very low relative pressure will play an important role in the future development of gas adsorption characterisation. 

Dossi et al. [61] loaded platinum in KL zeolite by vapor deposition of Pt(hfa)2 (hfa hexafluoroacetylacetonate). The organometallic precursor was sublimated at 70 °C in a flow of argon and adsorbed on the dehydrated KL zeolite. The decomposition of Pt(hfa)2 was achieved at 350°C in a H2-atmosphere. In situ EXAFS measurements suggested the formation of small clusters (Pt-Pt coordination number of 5), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements using CO as the probe molecule indicated the formation of carbonyl clusters of the general formula [Pt3(CO)g]n (n= 1 -4). 

We have developed a novel ultrasensitive detection method, thermal lens microscopy (TLM), for nonfluorescent species [13]. TLM is photothermal spectroscopy under an optical microscope. Our thermal lens microscope (TLM) has a dual-beam configuration excitation and probe beams [13]. The wavelength of the excitation beam is selected to coincide with an absorption band of the target molecule and that of the probe beam is chosen to be where the sample solution (both solvent and solute) has no absorption. For example, in determination of methyl red dye in water, cyclohexane, and n-octanol, a 514-nm emission line of an argon-ion laser and a 633-nm emission line of a helium-neon laser were used as excitation and probe beams, respectively [21], Figure 4 shows the configuration and principle of TLM [13]. The excitation beam was modulated at 1 kHz by an optical chopper. After the beam diameters were expanded, the excitation and probe beams were made coaxial by a dichroic mirror just before they were introduced into an objective lens whose magnification and numerical aper-... 

Specific surface areas and pore size distributions of mesoporous materials are best probed by nitrogen/argon adsorption and capillary condensation which will be outlined in detail below. It should be emphasized that the concept of specific surface area is not applicable when the size of the sorbed molecules approaches the diameter of the pore. Thus, for microporous substances values for specific surface areas have no physical meaning, but are rather characteristic of the volume of gas adsorbed. Nevertheless, these values are frequently used as practical numbers to compare the quality and porosity of microporous materials. The average pore size of microporous materials has to be probed by size exclusion measurements. For this purpose the uptake of a series of sorbates with increasing minimal kinetic diameter on a solid are explored. The drop in the adsorbed amount with increasing size of the sorbate defines the minimum pore diameter of the tested solid. The method will be described in detail below. 

Nb2Bri0 and MI5 have been determined.445 MX5 (X = C1, Br) molecules were studied in argon and dinitrogen matrices at low temperature and probed by IR spectroscopy (Section 4.5.2.6.2).413... 

Figure 9.4 Schematic of Fast Atom Bombardment. A stream of inert atoms (argon or xenon) strike a probe target on which analyte molecules of interest are dissolved in a liquid matrix (frequently glycerol). The fast stream of inert atoms is created by electron bombardment of inert atoms to create ions that are accelerated by a potential difference. Kinetic energy is transferred from ions to more inert atoms leading to the stream of fast atoms that act to sputter molecular and fragment ion species into the vapour phase for mass analysis.

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