Search results for "Wave"

Determination of concentrations in ternary and quaternary molecular gas mixtures using femtosecond Raman spectroscopy

2002

Measurements of concentrations in gas mixtures of three and four molecular components are presented. They rely on a femtosecond time-resolved pump–probe technique based on Raman-induced polarization spectroscopy. The rotational time response of the molecular gas mixture is measured as a function of the pump–probe time delay. No selective frequency tunability is needed as the molecular rotational spectra are excited within the laser bandwidth. The results obtained from experiments performed at room temperature in N2O–CO2–N2 and N2O–CO2–O2–N2 mixtures are presented and the accuracy of the method is discussed. Copyright © 2002 John Wiley & Sons, Ltd.

Studies of electron heating on a 6.4 GHz ECR ion source through measurement of diamagnetic current and plasma bremsstrahlung

2011

Diamagnetic current and low energy (2–70 keV) x-ray bremsstrahlung measurements taken on a 6.4 GHz electron cyclotron resonance ion source (ECRIS) are presented as a function of microwave power, neutral gas pressure and magnetic field configuration. X-ray flux from confined electrons and plasma energy density depend logarithmically on microwave power. This result differs from previous studies performed on ECRISs that operate at higher microwave frequencies, in which the x-ray power increases in an essentially linear fashion with the microwave power. X-ray power and plasma energy density both saturate as the neutral pressure is increased beyond a certain value. The gradient of the magnetic f…

New Calibration Model: Combining Integrated Calibration Method and H-point Standard Addition Method to Detect and Avoid Interference Effects

2018

A new calibration methodology based on the combination of integrated calibration method (ICM) and the H-point standard addition method (HPSAM) is presented. It allows the diagnosis and correction o...

Interacting induced dipoles polarization model for molecular polarizabilities. Reference molecules, amino acids and model peptides

1999

Abstract We outline a method for the calculation of molecular dipole ( μ ) and quadrupole ( Θ = ) moments and dipole–dipole polarizabilities ( α = ) which we have successfully applied to a series of reference molecules, amino acids and model peptides. The results for μ are in line with CPHF reference calculations. In particular, the calculated positive value of CO is in agreement with both experimental and CI calculations. The computation of ( α = ) has been performed by the interacting induced dipoles polarization model that calculates tensor effective anisotropic point polarizabilities (method of Applequist et al.). The POLAR program cannot be used as a black box. Some tests should be per…

Analytic calculation of the diagonal Born-Oppenheimer correction within configuration-interaction and coupled-cluster theory

2006

Schemes for the analytic calculation of the diagonal Born-Oppenheimer correction (DBOC) are formulated and implemented for use with general single-reference configuration-interaction and coupled-cluster wave function models. Calculations are reported to demonstrate the convergence of the DBOC with respect to electron-correlation treatment and basis set as well as to investigate the size-consistency error in configuration-interaction calculations of the DBOC. The importance of electron-correlation contributions to the DBOC is illustrated in the computation of the corresponding corrections for the reaction energy and activation barrier of the F + H2 --FH + H reaction as well as of the atomiza…

A MRCI PS and CASSCF study of the ground state MgO dissociation energy

1991

Abstract Ab initio calculations at CASSCF and MRCI PS levels are used to determine the dissociation energy for the X 1 Σ + state of MgO, which adiabatically dissociates to the ground state 1 S g of magnesium and to the excited 1 D g state of oxygen, as well as other spectroscopic parameters. Emphasis is placed upon the problem of properly selecting an adequate active space in CASSCF calculations and upon the improvements obtained in MRCI by selecting perturbatively the most important contributions to the total wavefunction and evaluating the remaining ones only by perturbational method. Through a procedure based on stabilizing the computed dissociation energy, values of 3.87 eV (MRCI PS) an…

Key Ingredients for Mastery of Chemical Microwave Processes

2012

A semi-empirical extrapolation technique for atomic and molecular properties derived from correlated wavefunctions

1976

Abstract A semi-empirical extrapolation technique is suggested for recovering the correlation defect remaining in atomic and molecular properties calculated from highly correlated wavefunctions. These procedures are applied to PNO-CEPA and PNO-IPPA calculations on F, F + , F − , and HF in order to obtain “exact” estimates of the ionization potential, electron affinity, and dissociation energy.

Radiation-induced defects and their recombination processes in the x-ray storage phosphor BaBr2:Eu2 

2003

The recombination processes in the x-ray storage phosphor BaBr2:Eu2+ were investigated by optical and magneto-optical methods. A structure-sensitive investigation of the defects involved in the recombination processes was performed by detecting the microwave-induced changes in the recombination luminescence in a high magnetic field. F centres as well as VK hole centres are created after x-irradiation at low temperatures. The low-energy recombination band peaking at about 460 nm is due to F–VK centre recombinations, whereas the two high energy bands at 282 and 315 nm are probably due to recombinations of self-trapped excitons.

Theoretical study of the electronic spectrum of magnesium-porphyrin

1999

Multiconfigurational self-consistent field (SCF) and second order perturbation methods have been used to study the electronic spectrum of magnesium-porphyrin (MgP). An extended ANO-type basis set including polarization functions on all heavy atoms has been used. Four allowed singlet states of E1u symmetry have been computed and in addition a number of forbidden transitions and a few triplet states. The results lead to a consistent interpretation of the electronic spectrum, where the Q band contains one transition, the B band two, and the N band one. The computed transition energies are consistently between 0.1 and 0.5 too low compared to the measured band maxima. The source of the discrepan…