摘要:

where the separationRis measured in units ofc0. The coefficient ofR-6agrees with the calculations of Pauling and Beach but the coefficient ofR-8is quite different from theirs. The wave function is greatly simplified by introducing natural orbitals. If the wave function is approximated by using only one or two sets of natural orbitals, very little error results in the calculated dispersion energy. Also, it is shown that such an approximation leads to very little error in the mean square deviation of the approximate wave function from the exact function. This illustrates the theorem that an approximate wave function composed ofnnatural orbitals has a smaller mean square deviation from the true function than an approximate wave function made up fromnother sorts of orbitals. An application of long-range intermolecular force calculations to collision theory is also given.

ISSN:0026-8976    

DOI:10.1080/00268975900100231

出版商:Taylor & Francis Group    

年代:1959

数据来源: Taylor

摘要:

Vibrational transition probabilities have been calculated by the Schwartz, Slawsky and Herzfeld method [3] for the deactivation of HO2* in collision with H2, O2and CO2. The relative efficiencies of H2, O2and CO2are compared with their third-body efficiencies found experimentally and it is concluded that the transfer of large vibrational quanta from HO2* is unlikely to play an important part in determining the position of the second explosion limit of the H2/O2reaction. This conclusion is at variance with the explanation put forward by Walsh [1] of the ‘anomalous’ third-body efficiencies of H2O and CO2in this reaction.

ISSN:0026-8976    

DOI:10.1080/00268975900100241

出版商:Taylor & Francis Group    

年代:1959

数据来源: Taylor

摘要:

The rate of approach to the steady state in a convection-free two-bulb thermal diffusion experiment is treated in a more rigorous manner than previously available, in order that reliable ordinary diffusion coefficients may be derived from thermal diffusion measurements. The final results are of the same form as in the original simplified Jones and Furry treatment, but the parameters are now interpreted somewhat differently and a new correction term appears. Application to Nettley's measurements on H2-N2mixtures removes an apparent discrepancy with the kinetic theory prediction of the composition dependence of the diffusion coefficient for this system.

ISSN:0026-8976    

DOI:10.1080/00268975900100251

出版商:Taylor & Francis Group    

年代:1959

数据来源: Taylor

摘要:

The pairing of Hückel molecular orbitals in an alternant hydrocarbon holds in a more general sense for wave functions which make complete allowance for the correlation of π electrons within the atomic orbital scheme. The new pairing property holds exactly in the scope of Pariser, Parr, and Pople's approximations, and leads to an exact correspondence between every detail of the excited states, the electronic spectra and electron resonance spectra of positive and negative hydrocarbon ions. Neutral molecules have a half-filled electron shell in which electrons and holes are on an equal footing. This causes the electron distribution to be uniform in every electronic state, and leads to two kinds of excited state—‘even’ and ‘odd’—as Pariser first suggested. Transitions between states of the same parity are forbidden. In neutral radicals the spin density vanishes in all the bonds, and in both radicals and molecules the bond orders vanish between atoms of the same set (starred or unstarred).

ISSN:0026-8976    

DOI:10.1080/00268975900100261

出版商:Taylor & Francis Group    

年代:1959

数据来源: Taylor

摘要:

It is shown that γ rays act on glycine to give the free radical NH3+-ĊH-CO2−which remains trapped in the solid. Electron spin resonance spectra from an irradiated single glycine crystal show marked anisotropy and it is deduced that the radicals are precisely oriented in the crystal lattice. The symmetry shown by the spectra is consistent with that of the crystal lattice. Despite overlapping of lines, the spectra due to the NH3+-ĊH-CO2−radical have been interpreted in terms of electronnucleus coupling tensors for the N, the H(C)and the three H(N)nuclei, the latter being equivalent by virtue of a rotation or tunnelling of the -NH3+grouping. A qualitative interpretation of these tensors in terms of the electronic structure of the radical is given. This is consistent with the negative spin density on the H(C)atoms and a positive spin density on the H(N)atoms, as predicted by theoretical treatments. The radicals appear to be oriented in the lattice in approximately the same way as their parent molecules.

ISSN:0026-8976    

DOI:10.1080/00268975900100271

出版商:Taylor & Francis Group    

年代:1959

数据来源: Taylor

摘要:

Chemical shifts are recorded for the thallium resonance of203Tl and205Tl in a number of thallium compounds in the solid state and in aqueous solutions. Different chemical shifts are found for Tl+, TlCl4′ and TlCl6…'. Solid Tl2Cl3shows two thallium resonances with intensities in the ratio 3 : 1, consistent with the formula Tl3(TlCl6). Hydrated thallic chloride in the solid state shows three thallium resonances which may be due to the presence of Tl(H2O)x+++, TlCl4′ and TlCl6…'. The chemical shifts of the thallium resonance in aqueous thallic chloride and bromide solutions in the presence of added halides are consistent with the stepwise formation of complex ions. The second moments of the resonances of the two thallium isotopes in solid compounds shows that there is spin-spin coupling between the thallium isotopes, and a weak coupling in some cases between thallium nuclei and the nuclei of anions.

ISSN:0026-8976    

DOI:10.1080/00268975900100281

出版商:Taylor & Francis Group    

年代:1959

数据来源: Taylor

摘要:

The electron transfer spectra of the chloro, bromo, and iodo complexes of Ru(III), Ru(IV), Rh(III), Pd(IV), Sn(IV), Sb(V), W(VI), Re(IV), Os(III), Os(IV), Ir(III), Ir(IV), Pt(IV), and Pb(IV) are studied and interpreted by group-theoretical methods as transitions of π (and at higher wave-numbers, σ) electrons, mainly localized in the ligands, to the available orbitals of even parityγ5,γ3andγ1, representing mainlyd,d, andselectrons of the central ion. The half-widths and intensities of the bands support the identification. The remarkable similarity between the spectra ofd4andd5systems with the same set of ligands is explained by the presence of only one effective excited state of the central ion. The structure expected of the group of π transfer bands as function of increasing Landé parameter ζnpof the halogen is calculated. The use of pure molecular orbital (M.O.) configurations as a convenient classification (but not a very good approximation to the wave-function) is compared to the analogous case of atomic spectroscopy. It is recommended to estimate the M.O. energies from absorption spectra rather than to try to calculate them from unreliable approximations.

ISSN:0026-8976    

DOI:10.1080/00268975900100291

出版商:Taylor & Francis Group    

年代:1959

数据来源: Taylor