摘要:

A procedure is outlined by which one can get information about the effects of electronic excitation on the interactions between molecules. The absorption and emission spectra of impurities in molecular crystals, and specifically the mean positions and widths of the lines, are required as functions of temperature. A theory of M. Lax is used to relate mean position and width to intermolecular forces. The preliminary treatment of this problem by McCarty and Robinson is evaluated and extended: their procedure is expected to be valid for very narrow lines only.

ISSN:0026-8976    

DOI:10.1080/00268976000100361

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

Various refinements are added to a previous theoretical calculation of the configurational free energy of condensed mixtures ofo- andp-hydrogen, based on an oversimplified statistical model: (a) account is taken of the fact that the forces acting betweeno- andp-molecules are somewhat different and (b) the rigid lattice model previously used is replaced by an ensemble of Einstein oscillators. A better agreement with experiment is reached.

ISSN:0026-8976    

DOI:10.1080/00268976000100371

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

It is shown that there are two possible mechanisms whereby a singlet-triplet absorption band of a molecule can gain intensity under the perturbing influence of a paramagnetic species. The first involves some mixing of the triplet state with the singlet states of the molecule. The second involves a mixing of the triplet state with charge-transfer states of the complex formed between the molecule and the paramagnetic species. It is shown that in the particular case of an alternant hydrocarbon, the first singlet-triplet absorption band is unlikely to gain intensity by the first of these mechanisms. It follows by elimination that the charge-transfer mechanism is the more important. The available experimental evidence supports this viewpoint.

ISSN:0026-8976    

DOI:10.1080/00268976000100381

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The visible and ultra-violet absorption spectra of transition metal oxyanions are discussed in terms of a level scheme originally proposed for permanganate and chromate by Ballhausen and Liehr [4]. This level scheme is extended to oxyions containing one or two unpaired electrons and by group theoretical arguments and dipole strength calculations is shown to be consistent with experiment.

ISSN:0026-8976    

DOI:10.1080/00268976000100391

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

A quantum-mechanical study is made of the changes of the nuclear magnetic screening constantσand the diamagnetic susceptibilityXof two interacting hydrogen atoms due to van der Waals and overlap interatomic forces (effects of electron spin being neglected). At large distances the calculations show that van der Waals forces decrease the nuclear screening but increase the diamagnetic susceptibility (in magnitude). As the internuclear distance is reduced the first effect of overlap forces is to increase the screening in the repulsive (electronic triplet) state but this is followed by a further reduction. Attractive overlap forces (as in the ground state of H2) ultimately lead to an increase in screening.

ISSN:0026-8976    

DOI:10.1080/00268976000100401

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The interpretation of ABC-type spectra is discussed in relation to several series of calculated spectra; some frequency and intensity sum rules are indicated.

ISSN:0026-8976    

DOI:10.1080/00268976000100411

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

On irradiation of glassy solutions of aromatic hydrocarbon mono- and di-negative ions with ultra-violet light photo electron ejection occurs according to the reactions:

ISSN:0026-8976    

DOI:10.1080/00268976000100421

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

Starting from the Grand Partition Function and using matrix methods introduced previously, a formulation of the theory of helix-coil transitions in charged macromolecules is given. The theory is compared with experimental data for the system polyglutamic acid-dioxane-water-NaCl. If the parameter describing the extra difficulty associated with initiating a helical configuration is assigned the same value as for polybenzylglutamate, the calculations are in excellent agreement with experiment. An analysis of the physical significance of the Grand Partition Function leads to methods for determining the fraction of polymer in helical form, the equilibrium constant for the addition of a residue to an already formed helix, as well as the initiation parameter mentioned above. The value of the initiation parameter deduced from titration data on polyglutamic acid is in rough agreement with the value for polybenzylglutamate.

ISSN:0026-8976    

DOI:10.1080/00268976000100431

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor