scholarly journals Integral Absorption Coefficients of C−H Stretching Bands in IR Spectra of Ethane Adsorbed by Cationic Forms of Y Zeolite

2009 ◽  
Vol 113 (5) ◽  
pp. 839-844 ◽  
Author(s):  
I. R. Subbotina ◽  
V. B. Kazansky ◽  
J. Kröhnert ◽  
F. C. Jentoft
2019 ◽  
Vol 492 (1) ◽  
pp. 283-293 ◽  
Author(s):  
Reggie L Hudson ◽  
Robert F Ferrante

ABSTRACT Acetaldehyde is of interest to astrochemists for its relevance to both interstellar and cometary chemistry, but little infrared (IR) spectral data have been published for the solid phases of this compound. Here we present IR spectra of three forms of solid acetaldehyde, with spectra for one form being published for the first time. Direct measurements of band strengths and absorption coefficients also are reported for the first time for amorphous aldehyde, the form of greatest interest for astrochemical work. An acetaldehyde band strength at ∼1350 cm−1 that has been used as a reference for about 20 yr is seen to be in error by about 80 per cent when compared to the direct measurements presented here. Spectra and peak positions also are presented for H13C(O)13CH3, and then used for the first identification of ketene as a radiation product of solid acetaldehyde.


Author(s):  
Clifford S. Rainey

The spatial distribution of V and Ni deposited within fluidized catalytic cracking (FCC) catalyst is studied because these metals contribute to catalyst deactivation. Y zeolite in FCC microspheres are high SiO2 aluminosilicates with molecular-sized channels that contain a mixture of lanthanoids. They must withstand high regeneration temperatures and retain acid sites needed for cracking of hydrocarbons, a process essential for efficient gasoline production. Zeolite in combination with V to form vanadates, or less diffusion in the channels due to coke formation, may deactivate catalyst. Other factors such as metal "skins", microsphere sintering, and attrition may also be involved. SEM of FCC fracture surfaces, AEM of Y zeolite, and electron microscopy of this work are developed to better understand and minimize catalyst deactivation.


Author(s):  
M. E. Twigg ◽  
B. R. Bennett ◽  
J. R. Waterman ◽  
J. L. Davis ◽  
B. V. Shanabrook ◽  
...  

Recently, the GaSb/InAs superlattice system has received renewed attention. The interest stems from a model demonstrating that short period Ga1-xInxSb/InAs superlattices will have both a band gap less than 100 meV and high optical absorption coefficients, principal requirements for infrared detector applications. Because this superlattice system contains two species of cations and anions, it is possible to prepare either InSb-like or GaAs-like interfaces. As such, the system presents a unique opportunity to examine interfacial properties.We used molecular beam epitaxy (MBE) to prepare an extensive set of GaSb/InAs superlattices grown on an GaSb buffer, which, in turn had been grown on a (100) GaAs substrate. Through appropriate shutter sequences, the interfaces were directed to assume either an InSb-like or GaAs-like character. These superlattices were then studied with a variety of ex-situ probes such as x-ray diffraction and Raman spectroscopy. These probes confirmed that, indeed, predominantly InSb-like and GaAs-like interfaces had been achieved.


Author(s):  
Leonid E. Paramonov

A method for retrieving the absorption coefficients of Spirulina platensis pigments using absorption spectra of native cells and excluding the use of extracts is considered. Estimates of the intracellular concentration of chlorophyll a, С-phycoerythrin, С- phycocyanin and allophycocyanin in native cells are discussed.


2002 ◽  
Vol 715 ◽  
Author(s):  
Keda Wang ◽  
Haoyue Zhang ◽  
Jian Zhang ◽  
Jessica M. Owens ◽  
Jennifer Weinberg-Wolf ◽  
...  

Abstracta-Si:H films were prepared by hot wire chemical vapor deposition. One group was deposited at a substrate temperature of Ts=250°C with varied hydrogen-dilution ratio, 0<R<10; the other group was deposited with fixed R=3 but a varied Ts from 150 to 550°C. IR, Raman and PL spectra were studied. The Raman results indicate that there is a threshold value for the microstructure transition from a- to μc-Si. The threshold is found to be R ≈ 2 at Ts = 250°C and Ts ≈ 200°C at R=3. The IR absorption of Si-H at 640 cm-1 was used to calculate the hydrogen content, CH. CH decreased monotonically when either R or Ts increased. The Si-H stretching mode contains two peaks at 2000 and 2090 cm-1. The ratio of the integral absorption peaks I2090/(I2090+I2090) showed a sudden increase at the threshold of microcrystallinity. At the same threshold, the PL features also indicate a sudden change from a- to μc-Si., i.e. the low energy PL band becomes dominant and the PL total intensity decreases. We attribute the above IR and PL changes to the contribution of microcrystallinity, especially the c-Si gain-boundaries.


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