scholarly journals QUENCHING OF THE FLUORESCENCE BACKGROUND IN Cd0.96Zn0.04Te RAMAN SPECTRUM AT LOW TEMPERATURES

2001 ◽  
Vol 50 (5) ◽  
pp. 968
Author(s):  
PEI HUI-YUAN ◽  
FANG JIA-XIONG
Keyword(s):  
Raman Spectrum ◽  
Low Temperatures

Vibrational spectra and rotational isomerism of ethanethiol and ethanethiol-D1

1985 ◽  
Vol 63 (7) ◽  
pp. 1708-1712 ◽  
Author(s):  
Hans Wolff ◽  
Jerzy Szydlowski
Keyword(s):  
Raman Spectrum ◽  
Infrared Spectra ◽  
Low Temperatures ◽  
Room Temperature ◽  
Rotational Isomerism ◽  
Simultaneous Presence ◽  
Bending Vibration ◽  
Doublet Structure ◽  
Vibrational Bands ◽  
Rocking Vibration

The infrared spectra of gaseous, liquid, and solid C2H5SD, and the Raman spectrum of the liquid compound are analyzed and the corresponding spectra of C2H5SH were reinvestigated under improved conditions. In the deuterated compound the CH2 rocking vibration does not interact with the SD bending vibration and therefore does not split into vibrations of the conformers. The measurements suggest for gaseous and liquid C2H5SH and C2H5SD the simultaneous presence of the trans and gauche conformers, appearing at room temperature in the ratio of the order of 1:3. In analogy to solid C2H5SH, the exclusive presence of the gauche conformers can be inferred for solid C2H5SD. The spectra reported in the literature for the C2H5SH molecules embedded in matrices at low temperatures permit a similar interpretation. The doublet structure observed for the vibrational bands, not only of pure solid C2H5SH and C2H5SD but also of their solid mixtures, may be due to non-equivalent sites of the unit cell.

scholarly journals Experiments on the raman effect at very low temperatures

1933 ◽  
Vol 141 (845) ◽  
pp. 535-549 ◽  
Keyword(s):  
Raman Spectrum ◽  
Raman Spectra ◽  
Low Temperatures ◽  
Vibrational Energy ◽  
Raman Effect ◽  
Energy Levels ◽  
Solid Carbon Dioxide ◽  
Nitrogen Tetroxide ◽  
Primary Object ◽  
Vibrational Energy Levels

Hitherto, the experiments which have been carried out oil the Raman effect at low temperatures have been performed on substances of which the Raman spectra were unobtainable, or only obtainable with difficulty, at ordinary temperatures. Thus Daure* has obtained the Raman spectra of liquid methane, ethylene, ethane, propane, and ammonia, while McLennan and his co-workers have studied those of liquid hydrogen, oxygen, nitrogen, methane, helium, nitrous oxide and solid carbon dioxide. The primary object in these researches was to obtain the spectrum of the substance, and the influence of temperature on the spectrum has received very little attention. While the present work began as an attempt to obtain the Raman spectrum of nitrogen tetroxide, it has become increasingly evident in the course of it that the study of Raman spectra at very low temperatures may well prove to be a very fruitful field of research. It is clear that there will be at least two distinct possible effects of a change in temperature of the scattering substance on its Raman spectrum. If the change in temperature causes a change in the molecular structure of the substance (such as association of simple molecules into more complex aggregates, or a change in the crystalline form of the substance), then one may expect the appearance of new lines in the spectrum. Secondly, a change in temperature will result in a new distribution of the molecules in the various rotational and vibrational energy levels ; the effect of this will be to alter the character of the individual lines and bands in the spectrum without, however, giving rise to any new lines. The following paper gives a description of a new and very simple apparatus for the observation of Raman spectra at low temperatures, together with the results and discussion of the preliminary experiments on a few simple substances.

Interpretation of irradiation-induced changes in electron diffractograms and images of extinction contours at low temperatures

1984 ◽  
Vol 42 ◽  
pp. 268-269
Author(s):  
E. Knapek ◽  
H. Formanek ◽  
G. Lefranc ◽  
I. Dietrich
Keyword(s):  
Low Temperatures ◽  
Carbon Films ◽  
Organic Crystals ◽  
Wide Spread ◽  
Lens System ◽  
Preparation Conditions ◽  
Thin Carbon ◽  
Electron Diffractograms ◽  
Diffraction Patterns ◽  
Induced Changes

A few years ago results on cryoprotection of L-valine were reported, where the values of the critical fluence De i.e, the electron exposure which decreases the intensity of the diffraction reflections by a factor e, amounted to the order of 2000 + 1000 e/nm2. In the meantime a discrepancy arose, since several groups published De values between 100 e/nm2 and 1200 e/nm2 /1 - 4/. This disagreement and particularly the wide spread of the results induced us to investigate more thoroughly the behaviour of organic crystals at very low temperatures during electron irradiation.For this purpose large L-valine crystals with homogenuous thickness were deposited on holey carbon films, thin carbon films or Au-coated holey carbon films. These specimens were cooled down to nearly liquid helium temperature in an electron microscope with a superconducting lens system and irradiated with 200 keU-electrons. The progress of radiation damage under different preparation conditions has been observed with series of electron diffraction patterns and direct images of extinction contours.

Radiation Damage of Support Films

1981 ◽  
Vol 39 ◽  
pp. 28-29
Author(s):  
H.A. Cohen ◽  
W. Chiu
Keyword(s):  
Transfer Function ◽  
Low Temperatures ◽  
Carbon Support ◽  
Contrast Transfer Function ◽  
Electron Dose ◽  
Imaging Parameters ◽  
Negative Stain ◽  
Phase Corrections ◽  
Two Parameters ◽  
Medium Dose

The goal of imaging the finest detail possible in biological specimens leads to contradictory requirements for the choice of an electron dose. The dose should be as low as possible to minimize object damage, yet as high as possible to optimize image statistics. For specimens that are protected by low temperatures or for which the low resolution associated with negative stain is acceptable, the first condition may be partially relaxed, allowing the use of (for example) 6 to 10 e/Å2. However, this medium dose is marginal for obtaining the contrast transfer function (CTF) of the microscope, which is necessary to allow phase corrections to the image. We have explored two parameters that affect the CTF under medium dose conditions.Figure 1 displays the CTF for carbon (C, row 1) and triafol plus carbon (T+C, row 2). For any column, the images to which the CTF correspond were from a carbon covered hole (C) and the adjacent triafol plus carbon support film (T+C), both recorded on the same micrograph; therefore the imaging parameters of defocus, illumination angle, and electron statistics were identical.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

Ultrastructure of the soil fungus, Geomyces pannorus

1984 ◽  
Vol 42 ◽  
pp. 738-739
Author(s):  
J. A. Traquair ◽  
E. G. Kokko
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fine Structure ◽  
Low Temperatures ◽  
Soil Fungus ◽  
Organic Soils ◽  
Anatomical Studies ◽  
Transmission Electron ◽  
Electron Microscopical ◽  
Scanning Electron

With the advent of improved dehydration techniques, scanning electron microscopy has become routine in anatomical studies of fungi. Fine structure of hyphae and spore surfaces has been illustrated for many hyphomycetes, and yet, the ultrastructure of the ubiquitous soil fungus, Geomyces pannorus (Link) Sigler & Carmichael has been neglected. This presentation shows that scanning and transmission electron microscopical data must be correlated in resolving septal structure and conidial release in G. pannorus.Although it is reported to be cellulolytic but not keratinolytic, G. pannorus is found on human skin, animals, birds, mushrooms, dung, roots, and frozen meat in addition to various organic soils. In fact, it readily adapts to growth at low temperatures.

Sign in / Sign up

Export Citation Format

Share Document