摘要:

The effect of temperature, solvent, concentration of solute and quenching by oxygen on the decay time and fluorescence spectrum of naphthalene was investigated. At high solute concentrations (>0·1 M) an anomaly in the emission spectrum is interpreted as being due to transient dimers, whereas at lower solute concentrations (<0·1 M), no evidence has been found to support the assumption of transient dimers.

ISSN:0026-8976    

DOI:10.1080/00268976200100351

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

The 60 Mc/s proton resonance spectrum of 2,3-dibromopropionic acid is reported and analysed as an ABC system. The relative signs of the geminal and vicinal coupling constants observed have been determined by the double irradiation method and confirmed by experiments at 15·086 Mc/s. The two types of coupling constant are found to have opposite signs and to be large, the geminal one being ∓9·9 c.p.s. and the vicinal ones ±10·8 c.p.s. and ±4·6 c.p.s.

ISSN:0026-8976    

DOI:10.1080/00268976200100361

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

The indirect proton spin-spin coupling (J) in acetaldehyde has been measured with an accuracy of ±0·01 c.p.s. over the temperature range -119°c to +52°c. The small change of 0·15 c.p.s. is interpreted in terms of the internal motion of the molecule which gives an average ofJover its angular thermally excited motion in a three-well potential. The constant and cos 3ϕ terms inJ(ϕ) are determined and an estimate ofJ(ϕ) is made. It is pointed out that the zero point internal vibration in this and similar molecules may be important for the comparison of experimental and theoreticalJvalues. AlthoughJfalls with increasing temperature in acetaldehyde it may well rise in other similar molecules.

ISSN:0026-8976    

DOI:10.1080/00268976200100371

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

It is shown that no arbitrary distortion of an octahedral complex can provide a first-order contribution to the optical rotation and that this result is also true for certain other complexes of high symmetry. The second-order effects of the odd parity ligand field are investigated for the Co(en)33+ion (en = ethylenediamine) and found to provide a reasonably satisfactory explanation of the higher wavelength part of the optical rotatory dispersion curve.

ISSN:0026-8976    

DOI:10.1080/00268976200100381

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

A new experimental criterion is advanced for magnetic dipole allowed transitions of electrons in polyatomic molecules, based upon the relative band areas of the circular dichroism and of the corresponding unpolarized absorption given by the chromophores of optically active compounds. The 3000 Å carbonyl absorption is shown to be magnetic dipole allowed, although most of the absorption intensity derives from a vibrationally induced or stereochemically determined charge transfer contribution, which has an electric dipole moment with a component directed parallel to the carbonyl bond axis in optically active ketones. The known features of the formaldehyde 3000 Å absorption are interpreted in terms of a magnetic dipole transition moment orientated along the carbonyl bond, and a charge transfer electric dipole moment directed perpendicular to that bond in the plane of the molecule, induced by the methylene out-of-plane bending vibration.

ISSN:0026-8976    

DOI:10.1080/00268976200100391

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

The proton chemical shifts of a number of relatively unstrained hydrocarbons have been analysed in terms of the local diamagnetic shielding and long-range shielding by carbon-carbon single bonds. The analysis suggests that the latter term is the dominant factor determining the relative chemical shifts, the most probable value of ΔXCCbeing near 7 × 10-30cm3molecule-1. The relative shifts of the methyl and methine protons ofmesoanddl2, 3-disubstituted butanes and axial and equatorial methyl groups in cyclohexane rings are discussed in relation to this value of ΔXCC.

ISSN:0026-8976    

DOI:10.1080/00268976200100401

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

The E.S.R. spectrum of potassium vanadyl oxalate has been measured in dilute solutions in a potassium titanyl oxalate crystal. The crystal contains one paramagnetic species and all the paramagnetic units in the crystal lie parallel to one another and are axially symmetric. There is no evidence of any interaction between different vanadyl ions so it appears that potassium vanadyl oxalate in the crystal is a monomer and not a dimer as has been postulated [1]. The hyperfine splitting constants confirm the predictions of ligand field theory as to the orbital occupied by the unpaired electron.

ISSN:0026-8976    

DOI:10.1080/00268976200100411

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

The optical and electron spin resonance spectra of molybdenum and tungsten octacyanides have been measured and the results are interpreted by electrostatic crystal field theory using a point charge model ofD2dsymmetry.

ISSN:0026-8976    

DOI:10.1080/00268976200100421

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

An attempt is made to account for the apparent bond alternation in the rings of dibenzene chromium in terms of a ‘pseudo Jahn-Teller effect’. The attempt fails.

ISSN:0026-8976    

DOI:10.1080/00268976200100431

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

As a direct result of the dynamical Jahn-Teller effect there may be strongl-type doubling of certain rotational sub-levels of electronically degenerate dihedral molecules. The expressions for the rotational levels unaffected by this doubling are formally identical with those derived for non-degenerate molecules, but the effective rotational and Coriolis coupling constants may vary erratically from one vibronic level to another.

ISSN:0026-8976    

DOI:10.1080/00268976200100441

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor