摘要:

The effects of intramolecular redistribution of vibrational energy on both the fate of an excited complex molecule and the appearance of its electronic spectra are discussed in terms of a three-dimensional energy surface. It is suggested that continuous absorption be used as a criterion for the application of classical methods to intra- and inter-molecular vibrational energy transfer in those cases where fluorescence emission is observed.

ISSN:0008-4042    

DOI:10.1139/v58-011

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The use of measurements of the products of flash photolysis as a means for studying the reactions of electronically-excited molecules is discussed. With intense light sources the problem of isolating these reactions from others involving free radicals is simplified. The flash sources also have their limitations, and misleading information which can result from the presence of inert gases is noted. A diagnostic test is proposed for detecting the effects (if any) of a possible adiabatic temperature rise of the flash.Some recent studies in the author's laboratory are summarized. Evidence is presented that in the flash photolysis of acetone acetyl radicals arise from an excited molecule. Several deactivation processes are described and compared with results from fluorescence studies.

ISSN:0008-4042    

DOI:10.1139/v58-012

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

When atomic sodium is diffused into a mixture of atomic and molecular hydrogen, a weak chemiluminescence is observed in the gas phase. Visible emission consists of the sodium D lines. The total intensity of the emission, ~5 × 1011 photons/second, indicates that only one in 5 × 104of the sodium atoms entering the reaction vessel is involved in luminescent reaction. In order to account for the rapid fall-off in intensity of the flame away from the nozzle it is necessary to suppose that some non-luminescent reaction is removing sodium atoms in the gas phase. Preliminary experiments suggest that the non-luminescent reaction is Na + H + H2 → NaH + H2, and the luminescent reaction either Na + Na + H → NaH + Na* with collision yield 4 × 10−3or Na + H + H → H2 + Na* with collision yield 1 × 10−5.

ISSN:0008-4042    

DOI:10.1139/v58-013

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The quenching of the iodine fluorescence spectrum by various inert gases and oxygen has been studied with a view to obtaining information on the efficiencies of vibration energy transfer processes in this system. Preliminary results here presented are in agreement with earlier work of Rössler and Eliaschevich and indicate that the transfer processes are very efficient. A kinetic scheme is proposed to account for the various possible quenching and transfer processes and it is shown that this is in agreement with experimental results.

ISSN:0008-4042    

DOI:10.1139/v58-014

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Quenching of I2*(υ′ = 26) is shown to take place to the exclusion of vibrational-energy transfer in iodine at pressures up to 19 mm. A possible quenching mechanism involving sensitized predissociation of the collision partner is described. Vibrational transfer in collisions with H2and D2is found to occur at less than every gas kinetic collision. Arguments on general grounds are put forward to support this result, which conflicts with that of earlier workers. Increase in the mass of the isotope is found to bring about increased efficiency of vibrational transfer

ISSN:0008-4042    

DOI:10.1139/v58-015

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Previous theories of acetylene pyrolysis are reviewed in the light of recent work by Minkoff, Newitt, and Rutledge. It is shown that the relatively large rates observed at the beginning of the induction period do not agree with mechanisms involving the intervention of comparatively stable dimers. The required kinetic form is obtained, however, if a triplet diradical is produced on the surface in a bimolecular process, followed by gas phase polymerization, with some chain ending on the surface. The detailed mechanism closely resembles Flory's scheme for liquid phase vinyl polymerization. The shape of the radical is discussed, and it is suggested that thetrans-configuration leads to polymerization, while thecisfacilitates dehydrogenation.

ISSN:0008-4042    

DOI:10.1139/v58-016

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Hexafluoroacetone vapor, when excited at 25 °C by light of wavelength 3130 Å, gives rise to fluorescence. The fluorescence spectrum starts at about 3470 Å and extends to almost 6000 Å with a maximum at about 4200 Å, independent of pressure over the range 3 mm. to 170 mm. No fine structure is observed. Oxygen has almost no effect on the spectrum, contrary to the cases of acetone and biacetyl vapor, where oxygen causes a marked change. The absorption follows Beer's law between 5 mm. and 50 mm. of hexafluoroacetone pressure and the absorption coefficient has been measured.The fluorescence efficiency decreases slightly with the addition of less than 1 mm. of oxygen and there stays constant up to an oxygen pressure of 30 mm., indicating that the fluorescence may be principally from the short-lived singlet excited state. The fluorescence efficiency increases with pressure of hexafluoroacetone or with the addition of inert gases such as perfluorobutane, perfluoropropane, hexafluoroethane, or carbon dioxide. The present results may be compared with those of the photolysis, where it was found that the quantum yield of the decomposition decreases with increasing pressure and with added inert gases. A close relationship between the fluorescence and the photolysis suggests itself. A mechanism is proposed to explain the results, which assumes that the molecule is raised to the upper vibrational levels of a singlet excited state, and subsequently deactivated to the lowest vibrational levels of the same state, from which it fluoresces. On the basis of this mechanism it seems possible to correlate the photolysis with the fluorescence.

ISSN:0008-4042    

DOI:10.1139/v58-017

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

ω-Amino alcohols possessing five or more methylene units between the amino and hydroxyl groups on condensation with carbon disulphide gave good yields of 1,3-di-(ω-hydroxyalkyl) thioureas. These symmetrically disubstituted thioureas on oxidation gave the corresponding 1,3-di-(ω-hydroxyalkyl) ureas.

ISSN:0008-4042    

DOI:10.1139/v58-018

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The infrared spectra of a number of malonate esters have been examined. Most of them exhibit two ester carbonyl stretching bands which have been shown not to be due to enolization and conjugate chelation or to association. The influence of α-substituents is discussed, as well as the reason for the splitting of the band.

ISSN:0008-4042    

DOI:10.1139/v58-019

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The stable free radical diphenylpicrylhydrazyl (DPP•) has been found to react quantitatively with ammonia and hydrazine forming nitrogen and diphenylpicrylhydrazine, and less cleanly with hydroxylamine forming diphenylpicrylhydrazine and nitrous oxide. The reactions of DPP• with a variety of amines are not clean, in part owing to the formation of complexes of the amines with the reaction product diphenylpicrylhydrazine. Preliminary investigations of the reactions of DPP• with mercaptans have shown that these otherwise clean reactions have a variable stoichiometry, dependent on the concentration and other reaction conditions.

ISSN:0008-4042    

DOI:10.1139/v58-020

出版商:NRC Research Press    

年代:1958

数据来源: NRC