Fourier transform diffusion

DRIFTS Diffuse reflectance infrared Fourier-transform Same as IR Same as IR... 

Willey R R 1976 Fourier transform infrared spectrophotometer for transmittance and diffuse reflectance measurements Appl. Spectrosc. 30 593-601... 

Lennard C J, Mazzella W D and Margot P A 1993 Some applioations of diffuse refleotanoe infrared Fourier transform speotrosoopy DRiFTS in forensio soienoe Analysis 21 M34-7... 

Kazayawoko M, Balatineoz J J and Woodhams R T 1997 Diffuse refleotanoe Fourier transform infrared speotra of wood fibers treated with maleated polypropylenes J. Appl. Polymer Sci. 66 1163-73... 

Zeine C and Grobe J 1997 Diffuse refleotanoe infrared Fourier transform DRIFT speotrosoopy in the preservation of historioal monuments studies on salt migration Mikrochim. Acta 125 279-82... 

Diffuse reflectance infrared Fourier transform spectroscopy... 

Diffuse reflection iavolves reflecting the iafrared beam off of a soHd sample, as ia specular reflectioa, but it is the aoaspecular portioa of the reflected radiatioa that is coUected. Whea an ftir spectrometer is used, diffuse reflection is caUed DRIFTS (diffuse reflectance iafrared Fourier-transform... 

The resolution of infra-red densitometry (IR-D) is on the other hand more in the region of some micrometers even with the use of IR-microscopes. The interface is also viewed from the side (Fig. 4d) and the density profile is obtained mostly between deuterated and protonated polymers. The strength of specific IR-bands is monitored during a scan across the interface to yield a concentration profile of species. While in the initial experiments on polyethylene diffusion the resolution was of the order of 60 pm [69] it has been improved e.g. in polystyrene diffusion experiments [70] to 10 pm by the application of a Fourier transform-IR-microscope. This technique is nicely suited to measure profiles on a micrometer scale as well as interdiffusion coefficients of polymers but it is far from reaching molecular resolution. 

Keilson-Storer kernel 17-19 Fourier transform 18 Gaussian distribution 18 impact theory 102. /-diffusion model 199 non-adiabatic relaxation 19-23 parameter T 22, 48 Q-branch band shape 116-22 Keilson-Storer model definition of kernel 201 general kinetic equation 118 one-dimensional 15 weak collision limit 108 kinetic equations 128 appendix 273-4 Markovian simplification 96 Kubo, spectral narrowing 152... 

The diffusion equation describes the evolution of the mean test particle density h(r,t) at point r in the fluid at time t. Denoting the Fourier transform of the local density field by hk(t), in Fourier space the diffusion equation takes the form... 

Diffuse Reflectance IR Fourier Transform Spectroscopy (DRIFTS) can be employed with high surface area catalytic samples that are not sufficiently transparent to be studied in transmission. In this technique, the diffusely scattered IR radiation from a sample is collected, refocussed, and analysed. Samples can be measured in the form of loose powders. 

Diffuse reflectance infrared Fourier transform spectroscopy deuterium triglycine sulphate energy compensated atom probe energy dispersive analysis energy-loss near edge structure electron probe X-ray microanalysis elastic recoil detection analysis (see also FreS) electron spectroscopy for chemical analysis extended energy-loss fine structure field emission gun focused ion beam field ion microscope... 

Surface carbonites, carbonates, inorganic carboxylates and sometimes formates (specially at low temperature) were identified by Fourier transform infrared (FUR) [30,31], Step 3 Oxygen diffusion from the bulk sites to the surface... 

Although acetone was a major product, it was not observed by infrared spectroscopy. Flowing helium/acetone over the catalyst at room temperature gave a prominent carbonyl band at 1723 cm 1 (not show here). In this study, a DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) cell was placed in front of a fixed reactor DRIFTS only monitored the adsorbed and gaseous species in the front end of the catalyst bed. The absence of acetone s carbonyl IR band in Figure 3 and its presence in the reactor effluent suggest the following possibilities (i) acetone formation from partial oxidation is slower than epoxidation to form PO and/or (ii) acetone is produced from a secondary reaction of PO. 

The experimental system consists of three sections (i) a gas metering section with interconnected 4-port and 6-port valves, (ii) a reactor section including an in-situ diffused reflectance infrared Fourier transform spectroscopy reactor (DRIFTS) connected to tubular quartz reactor, (iii) an effluent gas analysis section including a mass spectrometer or a gas chromatograph (9). 

An important technical development of the PFG and STD experiments was introduced at the beginning of the 1990s the Diffusion Ordered Spectroscopy, that is DOSY.69 70 It provides a convenient way of displaying the molecular self-diffusion information in a bi-dimensional array, with the NMR spectrum in one dimension and the self-diffusion coefficient in the other. While the chemical-shift information is obtained by Fast Fourier Transformation (FFT) of the time domain data, the diffusion information is obtained by an Inverse Laplace Transformation (ILT) of the signal decay data. The goal of DOSY experiment is to separate species spectroscopically (not physically) present in a mixture of compounds for this reason, DOSY is also known as "NMR chromatography."... 

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