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Thomas B. Grimley 《Theoretical chemistry accounts》1987,72(5-6):475-484
A model for one-phonon thermal desorption is presented in which the structure of the substrate phonons, expressed as a projection on a surface atom of the phonon density of states, appears as a separate factor in the angle- and energy-resolved desorption rate. Desorption from both localized, and delocalized initioladatom states is considered. Under certain circumstances one can obtain the cosine-distribution of the equilibrium theory, but in general, the desorption flux from delocalized states deviates from the cosine law by being peaked away from the surface normal, whereas for localized initiol states, the flux is concentrated more in the normal direction. 相似文献
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T.B. Grimley 《Molecular physics》2013,111(3):329-336
A proof is given of the proposition that the intensity of the N.M.R. absorption line from a group of n equivalent protons is proportional to n. To do this, it has been necessary to satisfy the Pauli exclusion principle by classifying states according to the irreducible representations of the symmetric group. As far as spin is concerned, this classification is equivalent to one according to the value of I, the total spin. Degeneracy with respect to I, which would otherwise occur, is prohibited by the exclusion principle, and a correlation (not one-to-one) is established between I and the symmetries of the rotational states. 相似文献
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The resonance mechanism for positive and negative ionization of an atom reflected from a metal surface is treated in the time-dependent Hartree-Fock approximation assuming that the atom moves on its classical trajectory. A simple model is parameterized to describe 30–500 eV Na atoms reflected from tungsten, and the ionization probabilities are calculated by numerical integration of the equation of motion of the time evolution operator. Significant ionization can only occur if either the ionization level, or the affinity level of the atom crosses the Fermi level beyond the range of the atom-metal hopping interaction. On clean tungsten, the former situation applies, and the probability of positive ionization is nearly unity, and of negative ionization nearly zero. 相似文献
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A method for the calculation of the probability of neutralisation of an ion, which is scattered from the surface of a solid is presented. It assumes the ion to move along a classical trajectory and solves for the time evolution operator for the electronic system. For one electron Hamiltonians the solution can be carried out exactly. Results are presented for scattering from a semi-infinite linear chain. 相似文献
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Stimulated Raman spectroscopy is used to probe the photoexcitation dynamics of CO2-laser-excited SF6 in a molecular free-expansion jet. Time-dependent depletion of rotational levels in the ground state is observed by monitoring the ν1 Raman spectrum at various delay times after the CO2-laser excitation pulse. Optical Stark shifts are also seen, at short delay times, arising from resonances of the IR laser pulse with ν3 transitions from both ground and ν1 = 1 states. Molecules excited to the ν3 = 1 level are detected by scanning the ν1 + ν3 ? ν3 hot band. A direct determination of the anharmonicity X13 = ?2.910 ± 0.002 cm?1 is thus obtained. 相似文献
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Liaoran Cao Xinyu Zhang Alix Grimley Anna R. Lomasney Michael G. Roper 《Analytical and bioanalytical chemistry》2010,398(5):1985-1991
A microfluidic device was developed to produce temporal concentration gradients of multiple analytes. Four on-chip pumps delivered
pulses of three analytes and buffer to a 14-cm channel where the pulses were mixed to homogeneity. The final concentration
of each analyte was dependent on the temporal density of the pulses from each pump. The concentration of each analyte was
varied by changing the number of pump cycles from each reservoir while maintaining the total number of pump cycles per unit
time to ensure a constant total flow rate in the device. To gauge the independent nature of each pump, sinusoidal waves of
fluorescein concentration were produced from each pump with independent frequencies and amplitudes. The resulting fluorescence
intensity was compared with a theoretical summation of the waves and the experimental data matched the theoretical waves within
1%, indicating that the pumps were operating independently and outputting the correct frequency and amplitude. The device
was used to demonstrate the role of adenosine triphosphate-sensitive K+ channels in glucose-stimulated increases in intracellular [Ca2+] in islets of Langerhans. Perfusion of single islets of Langerhans with combinations of glucose, diazoxide, and K+ resulted in intracellular Ca2+ patterns similar to what has been observed using conventional perfusion devices. The system will be useful in other studies
with islets of Langerhans, as well as other assays that require the modulation of multiple analytes in time. 相似文献
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The overcompleteness of the basis states when Anderson's Hamiltonian is applied to chemisorption is allowed for by using a pseudopotential to describe the atom-metal coupling. Some calculations for hydrogen on free-electron Al are reported. 相似文献
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Absolute reaction rates for F + HX and F + DX (X = I, Br, Cl) have been obtained by monitoring the rise time of HF (DF) vibrational fluorescence following multiphoton dissociation of SF6 in mixtures of HX (DX) and argon. The cross sections for reaction are, in units of 10?16 cm2, 4.37, 5.26, and 1.16 for HI, HBr, and HCl, respectively. The isotope effects kHX/kDX, are 1.29 ± 0.14, 1.29 ± 0.18, and 1.38 ± 0.29, respectively. 相似文献
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