Thermomodulation Study of 0–0 Exciton Absorption Bands in Anthracene

1978 ◽  
Vol 44 (2) ◽  
pp. 489-496 ◽  
Author(s):  
Atsuo Matsui ◽  
Kenichi Tomioka
Keyword(s):  
Exciton Absorption ◽  
Absorption Bands

Temperature behavior of exciton absorption bands in layer semiconductors

2004 ◽  
Author(s):  
V. M. Kramar ◽  
N. K. Kramar ◽  
Bohdan M. Nitsowich
Keyword(s):  
Temperature Behavior ◽  
Exciton Absorption ◽  
Absorption Bands

Exciton spectra in thin crystals

1967 ◽  
Vol 298 (1452) ◽  
pp. 74-96 ◽  
Keyword(s):  
Crystal Size ◽  
Crystal Thickness ◽  
Optical Absorption Edge ◽  
Exciton Absorption ◽  
Molybdenum Disulphide ◽  
Absorption Bands ◽  
Observed Behaviour ◽  
Crystal Volume ◽  
Different Thickness ◽  
Split Valence

The optical absorption edge of crystals of molybdenum disulphide consists of two series of exciton absorption bands, the A and B series, which are due to the formation of delocalized excitons by direct allowed transitions from a split valence band. In ‘thick’ crystals at 77 °K the wavenumber position v n of the absorption bands is given by V n A = 15952 − ( 364 / n 2 ) c m − 1 and V n B = 18230 − ( 1056 / n 2 ) c m − 1 . Transmission and reflexion measurements on crystals of different thickness ranging from 0∙05 to 0∙8 μ m have shown that the exciton bands move to higher energies in thin crystals as a result of the increased exciton binding energy in small crystal volume. This effect is most marked for excitons of large radii and for the larger excitons of the A series. The variation of absorption coefficient and refractive index over the exciton spectra have been measured. The oscillator strength of the A series bands varies as ca . n -3 . Absorption bands A 1 and B 1 are unaffected by the crystal size effect and their observed behaviour in thin crystals is predicted by classical optics. This includes the measured oscillation in transmission with changing crystal thickness which occurs at the peaks of the n = 1 exciton bands.

Polarimetric Observations of Red Variables: A Study of Gas and Particle Interactions

1979 ◽  
Vol 46 ◽  
pp. 386-408 ◽  
Author(s):  
G. V. Coyne ◽  
I. S. McLean
Keyword(s):  
Wavelength Dependence ◽  
Stellar Atmosphere ◽  
Molecular Absorption ◽  
Absorption Bands ◽  
Absorption And Emission ◽  
Mira Variables ◽  
Stellar Photosphere ◽  
Regular Variable ◽  
Red Supergiants ◽  
Balmer Lines

AbstractIn recent years the wavelength, dependence of the polarization in a number of Mira variables, semi-regular variables and red supergiants has been measured with resolutions between 0.3 and 300 A over the range 3300 to 11000 A. Variations are seen across molecular absorption bands, especially TiO bands, and across atomic absorption and emission lines, especially the Balmer lines. In most cases one can ignore or it is possible to eliminate the effects due to interstellar polarization, so that one can study the polarization mechanisms operating in the stellar atmosphere and environment. The stars Omicron Ceti. (Mira), V CVn (semi-regular variable) and Mu Cephei (M2 la), in addition to other stars similar to them, will be discussed in some detail.Models to explain the observed polarization consider that the continuum flux is polarized either by electron, molecular and/or grain scattering or by temperature variations and/or geometrical asymmetries over the stellar photosphere. This polarized radiation is affected by atomic and molecular absorption and emission processes at various geometric depths in the stellar atmosphere and envelope. High resolution spectropolarimetry promises, therefore, to be a power-rul tool for studying stratification effects in these stars.

Investigation of the fine structure in overtone absorption bands of 12C2H4

1999 ◽  
Vol 97 (1) ◽  
pp. 265-277 ◽  
Author(s):  
M. BACH, R. GEORGES, M. HERMAN, A. PER
Keyword(s):  
Fine Structure ◽  
Absorption Bands

Neutral Lipids of Oats Fruit (Avena Sativa L.)

2020 ◽  
Vol 9 (4) ◽  
pp. 40-43
Author(s):  
N. K. Yuldasheva ◽  
S. D. Gusakova ◽  
D. Kh. Nurullaeva ◽  
N. T. Farmanova ◽  
R. P. Zakirova ◽  
...  
Keyword(s):  
Avena Sativa ◽  
Neutral Lipids ◽  
The Body ◽  
Biologically Active ◽  
Absorption Bands ◽  
Vital Functions ◽  
The Republic ◽  
Living Organisms ◽  
Main Components ◽  
Active Substances

Introduction. Lipids are a widespread group of biologically active substances in nature, making up the bulk of the organic substances of all living organisms. They accumulate in plants in seeds, as well as in fruits and perform a number of vital functions: they are the main components of cell membranes and the energy reserve for the body.Aim. Study of neutral lipids of sown oats (Avena sativa L.).Materials and methods. The objects of the study were fruits (grains) of oats of the sown variety "Tashkent 1," harvested in the Republic of Uzbekistan. Results and discussions. Neutral lipids of oat grains have been found to contain 13 fatty acids with a predominance of the sum of oleic, linolenic and linoleic acids. The total degree of unsaturation was almost 78%. Absorption bands characteristic of these substances were observed in the IR spectrum of MEGC.Conclusion. According to the results of the NL analysis, oat grains consisted of triacylglycerides and free LCDs, which were accompanied by hydrocarbons, phytosterols, triterpenoids and tocopherols.

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