摘要:

A coherent anti-Stokes Raman-scattering (CARS) study of the OH radical is conducted using resonance enhancement from the A2σ+-X2Π transition. A review of previous work on resonance-enhanced CARS is first given. The OH radical has specific one-photon spectral properties that lead to original CARS features; main and satellite CARS processes are thus defined at resonance. The use of resonance-enhanced CARS for the detection of OH is discussed. Optimum detectivity is obtained at triple resonance. Triple resonance can be nearly achieved using only two lasers on satellite CARS lines, but the best results are obtained on the main CARS lines using three lasers. This is verified experimentally in a discharge and in a one-atmosphere flat flame. Extra resonances from the excited electronic-state vibration are clearly seen. The results indicate that detection of OH in flames at high pressures should be easily feasible.

ISSN:0026-8976    

DOI:10.1080/00268979000100831

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Two algorithms are in common use for performing molecular-dynamics simulations of fluids composed of molecules with holonomic bond constraints. The SHAKE algorithm is widely used but is conceptually complex. The algorithm of Edberget al.(EEM), is simple in concept and structure except in regard to the manner in which numerical drift is handled. We describe a simple way of modifying the EEM method so that numerical drift in the holonomic constraints can be treated in a simple non-iterative fashion. The method is applied to fluids composed of planar molecules: liquid benzene and naphthalene. The results for the former system are in agreement with previous simulations using site-site potential models.

ISSN:0026-8976    

DOI:10.1080/00268979000100841

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268979000100851

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Diode-laser absorption spectra of a3Π CO between 1635 and 1780 cm-1have been measured in an a.c. discharge using population modulation detection, and assigned to vibration-rotation transitions of the fundamental and 1–2, 2–3, 3–4 hot bands in the Θ = 0, 1 and 2 fine structure states. The analysis was based on theR2model hamiltonian of Effantinet al.(1982) and thev= 0-4 data were fitted simultaneously with radio-frequency and microwave measurements, and with the perturbation by the a′3Σ+(v= 0) level included explicitly.

ISSN:0026-8976    

DOI:10.1080/00268979000100861

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Absorption, emission and laser induced fluorescence spectra of the YF molecule have been investigated. The new electronic transitions,b3Π-X1Σ, Θ = 1 -X1Σ,3Π-a3Δ,3Π-b3Π and3Π-X1Σ, have been observed. Following rotational analyses, the energies of the low-lyinga3Δ andb3Π states were found to beT0(a3Δ2) = 7987·03 andT0(b3Π1) = 11457·75 cm-1.

ISSN:0026-8976    

DOI:10.1080/00268979000100871

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

We study the Hall effect for ions in dilute electrolyte solutions by use of a continuum model and hydrodynamic equations that involve electric and magnetic force terms. We find that the problem is simplified by viewing the situation from the rest frame of a moving ion. This allows us to correct a calculation that we have presented earlier. We find that for stick boundary conditions the Lorentz force on an ion in a strongly polar liquid is reduced by about 44%.

ISSN:0026-8976    

DOI:10.1080/00268979000100881

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A theoretical method for the modelling of athermal freely jointed tangent hard-sphere chain fluids, of fixed lengthr, is developed based on a ‘particle-particle’ description of the chain system. This approach is based on the Percus-Yevick (PY) theory in the context of the particle-particle Ornstein-Zernike integral equation subject to some imposed connectivity constraints. Analytical expressions for the compressibility equations of state are derived for homonuclear chains, heteronuclear chains, blends or mixtures of homonuclear and heteronuclear chains, and homonuclear chains in a hard-sphere solvent. The PY compressibility equation of state for the athermal hard-sphere chain system is found to consist of (i) a non-bonded hard-sphere PY compressibility pressure contribution, and (ii) a PY bonding contribution due to chain formation. In the case of homonuclear chains the Percus-Yevick solution is found to yield excellent agreement with computer-simulation data reported in the literature. By replacing the PY hard-sphere compressibility pressure contribution with the Carnahan-Starling hard-sphere pressure, the accuracy of the PY bonding term for homonuclear chains is identified. We are, however, unable to determine the accuracy of the PY compressibility pressure of heteronuclear chains, chain mixtures and homonuclear chains in a hard-sphere solvent since computer-simulation data for these systems are not available.

ISSN:0026-8976    

DOI:10.1080/00268979000100891

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The symmetry properties of democratic three-body hyperspherical coordinates are derived by following the transformation at each stage of the defining sequence given by B. R. Johnson (1980,J. chem. Phys.,73,5051). The symmetries of the coordinates describing motion restricted to lie within a single fixed plane are investigated as a special case.

ISSN:0026-8976    

DOI:10.1080/00268979000100901

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Transitions in the fundamental and first hot bands of the GeH radical have been detected by CO laser magnetic resonance. Resonances from the four most abundant isotopes of germanium have been identified and fitted to determine the parameters of a single model Hamiltonian. All but the weakest signals were recorded with saturation (Lamb) dips.

ISSN:0026-8976    

DOI:10.1080/00268979000100911

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Fundamental and hot-band transitions of the GeD radical in its2∏ ground state have been detected by laser magnetic resonance. Transitions involving the three most abundant isotopes of germanium (70Ge,72Ge,74Ge) have been observed. A set of vibrational rotational constants for the ground state has been determined.

ISSN:0026-8976    

DOI:10.1080/00268979000100921

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor