Spectral Contours of Continuous Absorption Bands of Complex Molecules

1967 ◽  
Vol 47 (2) ◽  
pp. 758-761 ◽  
Author(s):  
H. Voorhof ◽  
H. Pollak
Keyword(s):  
Absorption Bands ◽  
Complex Molecules ◽  
Continuous Absorption

Absorption Cross Sections of Stratospheric Molecules

1974 ◽  
Vol 52 (8) ◽  
pp. 1465-1478 ◽  
Author(s):  
R. D. Hudson
Keyword(s):  
Absorption Spectrum ◽  
Solar Radiation ◽  
Band Structure ◽  
Molecular Oxygen ◽  
Cross Sections ◽  
Absorption Bands ◽  
Atmospheric Species ◽  
Continuous Absorption ◽  
Line Widths ◽  
The Cross

Photoabsorption cross sections necessary for calculations of the equilibrium conditions in the stratosphere fall into two distinct classes: cross sections for molecular oxygen and ozone, which control the transmission of solar radiation; cross sections for minor atmospheric species which are optically thin to solar radiation, and which are needed to calculate their rates of dissociation.The principal absorption features of molecular oxygen are absorption bands of the Schumann–Runge system between 175 and 200 nm and a weak dissociation continuum which extends from 175 to 260 nm. The band structure consists of many sharp rotational lines, and it is necessary to calculate cross sections using measured band parameters. Two measurements of the line widths for these bands have obtained large line widths (∼1 cm−1) indicating predissociation. The agreement between the two sets of data is good for only a few lines. This has implications in the calculation of the transmission of solar radiation to the lower stratosphere. The continua have been measured by four groups. The results agree, within the respective experimental errors, near 220 nm, but disagree near 250 nm.Ozone has a continuous absorption spectrum between 175 and 300 nm with band structure above 300 nm. Four sets of data are available which agree within ±2%. The cross section above 300 nm is temperature dependent. The cross sections for the minor species are in general not as well known. In nitric oxide, carbon monoxide, ammonia, and sulfur dioxide, band structure dominates the absorption spectrum, and cross sections have been measured at insufficient spectral resolution. Other species, such as nitric acid, hydrogen peroxide, water vapor, carbon dioxide, nitrous oxide, and nitrogen dioxide, have continua over the entire spectra range from 175 to 300 nm. Cross sections for these species have been measured; however, cross sections for many molecules, e.g., N2O5, NO3, etc., have not been studied.

Interpretation of the visible and near-infrared absorption spectra of compressed oxygen as collision-induced electronic transitions

1969 ◽  
Vol 47 (24) ◽  
pp. 2859-2871 ◽  
Author(s):  
G. C. Tabisz ◽  
Elizabeth J. Allin ◽  
H. L. Welsh
Keyword(s):  
Near Infrared ◽  
Low Frequency ◽  
Rotational Transition ◽  
Electronic Transitions ◽  
Absorption Bands ◽  
Specific Effects ◽  
Band Origin ◽  
Continuous Absorption ◽  
Compressed Gas ◽  
Large Width

The intensity profiles of some of the broad continuous absorption bands of oxygen in the near-infrared and visible regions were measured in the compressed gas over a range of pressures and temperatures. Three single electronic transitions (12 600, 10 600, 07620 Å) and three double transitions (6290, 5770, 4770 Å) were studied in detail. The asymmetry of the band profiles is shown to arise from a Boltzmann relation between the intensity distributions in the high and low frequency wings when the band origin is properly chosen. By assuming an appropriate rotational structure and broadening each rotational transition by a Boltzmann-modified dispersion curve the profiles of the bands could be reproduced with only minor discrepancies. These criteria, along with the well-known quadratic density dependence of the intensity, show that the bands are properly interpreted as collision-induced electronic transitions. The large width of the translational broadening functions required in the analysis indicates that the induction must be predominantly due to overlap interaction. No specific effects of (O2)2 complexes are identifiable in the spectra.

scholarly journals Final Remarks

1971 ◽  
Vol 2 ◽  
pp. 460-462
Author(s):  
J. L. Greenstein
Keyword(s):  
Solid Particle ◽  
Chemical Equilibrium ◽  
Diatomic Molecules ◽  
Polyatomic Molecules ◽  
Complex Molecules ◽  
Molecular Weights ◽  
Continuous Absorption ◽  
Technical Proficiency

It would be very ungracious not to say a few words about this remarkable set of presentations, even though it would be cruel to the audience to try to review them at this late hour. I made sixteen pages of summary notes of the highlights. We have heard about enormous improvements in our knowledge of the behavior of complex molecules in space. May I remind you that the computations of chemical equilibrium presented by Professor Klemperer covered largely the diatomic molecules known many years ago. The radio astronomers, with incredible technical proficiency, have found many polyatomic molecules with molecular weights close to a hundred; in a solid particle that causes continuous absorption we must reach weights near 108.

scholarly journals Physico-chemical studies of complex organic molecules. Part II.―Absorption spectra at low temperatures

1934 ◽  
Vol 115 (793) ◽  
pp. 274-278 ◽  
Keyword(s):  
Absorption Spectra ◽  
Low Temperatures ◽  
Atmospheric Temperature ◽  
Vibrational States ◽  
Absorption Bands ◽  
Complex Molecules ◽  
Physico Chemical ◽  
Stark Effects ◽  
Chemical Studies ◽  
Complex Organic

The physical criterion which has proved most valuable in distinguishing between different complex molecules is the absorption spectrum, but the absorption spectra have nearly always been measured in solution at ordinary temperatures, and usually give broad structureless bands. These bands frequently appear similar for different molecules, and are obviously unsatisfactory for the purpose of recognizing a particular molecule and distinguishing it uniquely. The ideal data for spectroscopic recognition are lines which are peculiar to a given atom or molecule. At low temperatures the bands of many molecules develop a structure with a considerable amount of detail (Kronenberger, 1930; Conant and Crawford, 1930; Arnold and Kistiakowsky, 1932; Spedding and Bear, 1933; Robertson, Fox, and Martin, 1934). This is probably due to two main factors: (i) the ground state of the molecule is simplified at low temperatures by the elimination of all but the vibrational states of lowest energy; and (ii) the Stark effects of the molecular fields of neighbouring molecules is rendered more constant as the molecules become quiescent, consequently the blurring is reduced. Both effects tend to diminish the width of the absorption bands and to bring out details of structure which cannot be recognized at atmospheric temperature. The development of structure will not be a property of all molecules; those, whose upper state of the electronic transition corresponds to dissociation or to "predissociation," will have bands continuous under all condition. But for a very large number of molecules, it should be possible to obtain structure at low temperatures, and in all cases narrowing of the bands should occur.

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.

Alkaline Dissociation Products of Lumbricus Terrestris Hemoglobin Viewed with the STEM

1981 ◽  
Vol 39 ◽  
pp. 434-435
Author(s):  
O. H. Kapp ◽  
M. Ohtsuki ◽  
N. Robin ◽  
S. N. Vinogradov ◽  
A. V. Crewe
Keyword(s):  
Carbon Film ◽  
Lumbricus Terrestris ◽  
Uranyl Acetate ◽  
Acetate Solution ◽  
Oxygen Carriers ◽  
Complex Molecules ◽  
Thin Carbon ◽  
Thin Carbon Film ◽  
Multiple Copies ◽  
Hill Coefficients

Annelid extracellular hemoglobins are among the largest known proteins (M.W = 3.9 x 106), and together with the hemocyanins are the largest known oxygen carriers. They display oxygen affinities generally higher than those o vertebrate hemoglobins with Hill coefficients ranging from slightly higher than unity to values as high as 5-6. These complex molecules are composed of multiple copies of as many as six different polypeptides and posse: approximately 150 hemes per molecule.The samples were diluted to 100-200 μg/ml with distilled water just before application to a thin carbon film (∽15 Å thick). One percent (w/v) uranyl acetate solution was used for negative staining for 2 minutes and dried in air. The specimens were examined with the high resolution STEM. Their general appearance is that of a hexagonal bilayer (Fig. 1), each layer consisting of six spheroidal subunits. The corner to corner hexagonal dimensic is approximately 300 Å and the bilayer thickness approximately 200 Å.

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
Sign in / Sign up

Export Citation Format

Share Document