scholarly journals The absorption spectrum of nitrous-oxide and the heat of dissociation of nitrogen

1932 ◽  
Vol 138 (834) ◽  
pp. 84-91 ◽  
Keyword(s):  
Nitrous Oxide ◽  
Absorption Spectrum ◽  
Wave Length ◽  
Accurate Estimation ◽  
Selective Absorption ◽  
Vapour State ◽  
Continuous Absorption ◽  
Band Absorption ◽  
Heat Of Dissociation

In some previous papers it has been shown by the author and others that saturated compounds of most substances in the vapour state show continuous absorption. A typical example is SO 3 -vapour, which was recently studied by the author and which enabled him to make an accurate estimation of the heat of dissociation of oxygen. In the present work, the absorption spectrum of N 2 O was investigated with a view to determining the heat of dissociation of nitrogen. Leifson was the first to investigate the absorption spectrum of N 2 O gas and found that the gas shows no selective absorption in the Schumann region. He states that the absorption is in the form of two continuous bands, the first extending from λ 2000 to λ 1680 and the second from λ 1550 beyond the range of observation. Recently Wulf and Melvin showed that when N 2 O is illuminated with light of wave-length λ 2300, it is decomposed photochemically into NO and N; they also noticed that N 2 O possesses no band absorption.

scholarly journals On the absorption spectrum of sulphur trioxide and the heat of dissociation of oxygen

1932 ◽  
Vol 137 (832) ◽  
pp. 366-372 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Wave Length ◽  
Continuous Light ◽  
Mass Action ◽  
Appreciable Change ◽  
Long Wave ◽  
Continuous Absorption ◽  
Quartz Spectrograph ◽  
Sulphur Trioxide ◽  
Heat Of Dissociation

Much work has been done by different workers on the heat of dissociation of oxygen and in the present work I have tried to determine this value from the continuous absorption spectrum of SO 3 -vapour. Experiment .-The absorption spectrum of the sulphur trioxide vapour was obtained with a hydrogen discharge tube as the source of continuous light. The photograph was taken on a Leiss quartz spectrograph. The SO 3 -vapour was prepared by distilling pure fuming sulphuric acid, the gas thus obtained being collected in a glass absorption tube, fitted with quartz ends. The ab­sorption was found to be continuous, beginning from the long wave-length ca . λ 3300, with no trace of bands which could be assigned to SO 3 , just as in the case of saturated halides. Different lengths of the tube as well as different pressures were tried with no appreciable change in the position of the long wave-length limit. As the SO 3 -vapour is normally partly dissociated into SO 2 and O 2 , generally some bands of the SO 3 gas appear. These can be easily eliminated by comparison with the absorption spectrum of SO 2 . But it is possible to eliminate the SO 2 bands from the plate by putting an excess of oxygen in the absorption chamber, and then filling it up with SO 3 -vapour. According to the law of mass action the partial pressure of SO 2 is very con­siderably reduced by the addition of O 2 , hence the bands due to SO 2 are expected to become weakened: this was found to be the case.

scholarly journals On the absorption of light by crystals

1938 ◽  
Vol 167 (930) ◽  
pp. 384-391 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Wave Length ◽  
Short Wave ◽  
Point Of View ◽  
Theoretical Point ◽  
Lattice Vibrations ◽  
Short Wave Length ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Positive Hole

The purpose of this paper is to discuss the absorption of light by non-metallic solids, and in particular the mechanism by which the energy of the light absorbed is converted into heat. If one considers from the theoretical point of view the absorption spectrum of an insulation crystal, one finds that it consists of a series of sharp lines leading up to a series limit, to the short wave-length side of which true continuous absorption sets in (Peierls 1932; Mott 1938). In practice the lattice vibrations will broaden the lines to a greater of less extent. When a quantum of radiation is absorbed in the region of true continuous absorption, a free electron in the conduction band and a "positive hole" are formed with enough energy to move away from one another and to take part in a photocurrent within the crystal. When, however, a quantum is absorbed in one of the absorption lines , the positive hole and electron formed do not have enough energy to separate, but move in one another's field in a quantized state. An electron in a crystal moving in the field of a positive hole has been termed by Frenkel (1936) an "exciton".

The absorption spectrum of liquid bromine

1937 ◽  
Vol 162 (910) ◽  
pp. 414-419 ◽  
Author(s):  
D. Porret ◽  
Frederick George Donnan
Keyword(s):  
Absorption Spectrum ◽  
Absorption Spectra ◽  
Ground State ◽  
Wave Length ◽  
Electronic States ◽  
Excited Electronic States ◽  
Long Wave ◽  
Liquid Bromine ◽  
Continuous Absorption ◽  
The Continuum

The continuous absorption spectra of gaseous bromine (Peskow 1917; Ribaud 1919; Gray and Style 1929; Acton, Aikin and Bayliss 1936) and of dissolved bromine (Bovis 1929; Gillam and Morton 1929) have been studied many times. They present a wide continuum (from about 30, 000 to 17, 000 cm. -1 .) with a maximum at 24, 000 cm. -1 . For the gas the continuum is preceded by two band systems on the long wave-length side. These systems converge at 19, 585 and 15, 896 cm. -1 . respectively. Acton, Aikin and Bayliss (1936) have shown that the continuum is not simple, and Mulliken (1936) and Darbyshire (1937) have pointed out that there are three overlapping continua corresponding to transitions from the ground state to three different excited electronic states. There are 3 II 0 + ← 1 Σ g , 3 II 1 ← 1 Σ g and 1 II ← 1 Σ g . The absorption spectrum of liquid bromine has been studied by Bovis (1929) form 18, 525 to 31, 750c cm. -1 . and by Camichel (1893) for two frequencies only (16, 978 and 18, 691 cm. -1 ).

scholarly journals The continuous absorption of light in potassium vapour

1928 ◽  
Vol 117 (777) ◽  
pp. 486-508 ◽  
Keyword(s):  
Vapour Pressure ◽  
Alkali Metals ◽  
Wave Length ◽  
Experimental Conditions ◽  
General Application ◽  
Continuous Absorption ◽  
Wide Range ◽  
Absorption Of Light ◽  
Relative Absorption ◽  
Band Absorption

While considerable attention has been paid to the line and band absorption of the alkali metals, very little work has been done on the continuous absorption. R. W. Wood and Holtzmark have observed the existence of this absorption, and Harrison has made some measurements on the continuous absorption of sodium in the region 2500 Å. U. - 2150 Å. U. In the present paper, results are given for potassium over a wide range of wave-length (4000 Å. U. - 2200 Å. U.) and under widely different experimental conditions. The ordinary methods of spectrophotometry have usually been designed to measure the absorption of solutions, etc., and are not suitable for measuring the absorption in a vapour unless the vapour pressure can be kept absolutely constant. A method of spectrophotometry has been developed by which it is possible to obtain measurements of the relative absorption coefficients for different wave-lengths correct to about 2 per cent, without keeping the vapour pressure absolutely constant. While the method is specially suitable for the measurement of an absorption which is not quite steady, it is really of quite general application.

scholarly journals On the absorption spectra of some higher oxides

1933 ◽  
Vol 139 (838) ◽  
pp. 397-405 ◽  
Keyword(s):  
Oxygen Atom ◽  
Absorption Spectra ◽  
Light Absorption ◽  
Wave Length ◽  
Long Wave ◽  
Continuous Absorption ◽  
The Difference ◽  
Heat Of Dissociation ◽  
Wave Limit ◽  
Excited Oxygen

Very little work has been done on the absorption spectra of the higher oxides, but recently, one of us has found that SO 3 gives a continuous absorption, beginning from a long wave limit, and after retransmission of a patch of light absorption again sets in. It was postulated that the first long wave limit of absorption by SO 3 marks the photochemical dissociation into SO 2 and normal oxygen atom, according to the equation SO 3 + hv 1 = SO 2 + O ( 3 P). (1) From this formula the heat of dissociation of oxygen was obtained with the help of some thermochemical data. The second long wave limit of absorption was attributed to the dissociation of SO 3 into SO 2 and excited oxygen, according to the process, SO 3 + hv 2 = SO 2 + O ( 1 D 2 ) (2) the difference between the two beginnings of absorption giving approximately the energy of excitation of oxygen from 3 P to 1 D 2 states. In this paper we have studied the absorption spectra of a few more higher oxides, viz., N 2 O 5 , TeO 3 , MoO 3 . As expected, all of them showed the same type of absorption as SO 3 . There was a first absorption on the long wave length side, followed by a patch of retransmitted light, which was again succeeded by a second region of absorption. The methods of procedure are described below.

scholarly journals The continuous absorption spectrum of hydrogen iodide

1936 ◽  
Vol 154 (881) ◽  
pp. 181-187 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Potential Energy ◽  
Potential Energy Curve ◽  
Hydrogen Bromide ◽  
Energy Curve ◽  
Band Spectrum ◽  
Distance Curve ◽  
A Value ◽  
Continuous Absorption ◽  
Heat Of Dissociation

For a molecule that exhibits a band spectrum it is possible to calculate the course of the potential energy internuclear distance curve for the upper state, from an analysis of the fine structure of the spectrum. In the present investigation, the upper potential energy curve has been calculated for a molecule which shows only continuous absorption, from the extinction coefficients of the absorption. The method employed is that used by Goodeve and Taylor in the interpretation of the continuous absorption spectrum of hydrogen bromide. From the convergence limit of a band system an exact correspondence is obtained with the heat of dissociation of the molecule into either excited or normal atoms. With molecules that absorb continuously, the “threshold of absorption” has sometimes been taken to give a value for this heat. This simple conclusion has, however, been found to be unsound, as the position of the “threshold” depends on the smallest amount of absorption that can be measured.

scholarly journals Short-Time Photodissociation Dynamics of 1-Chloro-2-Iodoethane From Resonance Raman Spectroscopy

1999 ◽  
Vol 19 (1-4) ◽  
pp. 71-74 ◽  
Author(s):  
Xuming Zheng ◽  
David Lee Phillips
Keyword(s):  
Raman Spectroscopy ◽  
Absorption Spectrum ◽  
Raman Spectra ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Time Dependent ◽  
Internal Excitation ◽  
Band Absorption ◽  
Resonance Raman Spectra ◽  
Short Time

We have obtained A-band absorption resonance Raman spectra of 1-chloro-2- iodoethane in cyclohexane solution. We have done preliminary time-dependent wavepacket calculations to simulate the resonance Raman intensities and absorption spectrum in order to learn more about the short-time photodissociation dynamics. We compare our preliminary results for 1-chloro-2-iodoethane with previous resonance Raman results for iodoethane and find that there appears to be more motion along non- C—I stretch modes for 1-chloro-2-iodoethane than for iodoethane. This is consistent with results of TOF photofragment spectroscopy experiments which indicate much more internal excitation of the photoproducts from 1-chloro-2-iodoethane photodissociation than the photoproducts from iodoethane photodissociation.

The absorption spectrum of SO and the flash photolysis of sulphur dioxide and sulphur trioxide

1959 ◽  
Vol 249 (1259) ◽  
pp. 498-512 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Dissociation Energy ◽  
Sulphur Dioxide ◽  
Flash Photolysis ◽  
Ultra Violet ◽  
Vibrationally Excited ◽  
A Value ◽  
Continuous Absorption ◽  
Sulphur Trioxide ◽  
Normal Spectrum

The flash photolysis of sulphur dioxide under adiabatic conditions results in the complete temporary disappearance of its spectrum , which then slowly regains its original intensity over a period of several milliseconds. Simultaneously with the disappearance of the sulphur dioxide spectrum a continuous absorption appears in the far ultra-violet and fades slowly as the sulphur dioxide reappears. It is shown that the effect of the flash is thermal rather than photochemical, and the possibility of the existence of an isomer of sulphur dioxide at high temperatures is discussed; the disappearance of the normal spectrum on flashing is explained in this way. Several previously unrecorded bands of SO observed in the photolysis indicate that the vibrational numbering of its spectrum should be revised by the addition of 2 to the present values of v' . This leads to a value of the dissociation energy of 123.5 kcal. In formation about the levels v' = 4, 5 and 6 has also been obtained. The isothermal flash photolysis of sulphur trioxide results in the appearance of vibrationally excited SO, and the primary photochemical step in this reaction is discussed.

scholarly journals A new method of spectrophotometry in the visible and ultra­violet and the absorption of light by silver bromide

1920 ◽  
Vol 97 (683) ◽  
pp. 181-190 ◽  
Keyword(s):  
Light Intensity ◽  
Photographic Plate ◽  
Wave Length ◽  
New Method ◽  
Silver Bromide ◽  
Selective Absorption ◽  
Quantitative Investigation ◽  
Advantages And Disadvantages ◽  
Absorption Of Light

A quantitative investigation of the absorption of light by silver bromide has been undertaken as a preliminary to a photochemical investigation of the action of silver bromide in the photographic dry plate. A good summary of the advantages and disadvantages of the various methods which have been devised by different experimenters for the quantitative investigation of the absorption of light by substances is given by Ewest in a thesis entitled, “Beiträge zur quantitativen Spectralphotographie,” of which an abstract is given by F. F. Renwick. All the methods which have been used previously either depend upon Schwarzschild’s law of the relation between time of exposure and the photographic effect, or a so-called neutral wedge is used which is supposed to absorb equally in all wave-lengths or is calibrated for selective absorption. The method which we have used is in some ways similar to that used by Ewest, but the apparatus required is very much simpler and a wedge of the material under examination is used instead of the neutral wedge of Ewest. In our method all that is required of the photographic plate is that the exposure of two adjacent portions of the same plate to the same light intensity of the same wave-length or the same time gives the same density under identical conditions of development. This condition is easily satisfied. As will be seen in the sequel, errors are reduced to errors in measurements of length.

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