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Helium Atom (helium + atom)
Selected AbstractsGeometrical properties of nodal surfaces of many-electron wave functionsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2010Nikolai D. Chuvylkin Abstract Hypothesis of the exclusion of equipotential surfaces for many-electron wave functions (MWF) has been enunciated. This hypothesis clarifies the physical meaning of the Pauli exclusion principle and opens the way for future progress of new quantum-chemical methods for the construction of approximate MWFs differing from the traditional Hartree,Fock approximation. The equipotential surface exclusion principle has been tested on traditional representative "test systems" of quantum mechanics: the helium atom, the lithium atom, and the hydrogen molecule. Judging by the results of these tests, the use of the suggested approach can lead to a considerable increase in the efficiency of high-accuracy quantum-chemical calculations. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Rydberg states of the helium atomINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 9 2009Jia Deng Abstract Using the recently introduced maximum overlap method and Hartree,Fock Perturbation Theory (HFPT), we compute Hartree,Fock (HF) wavefunctions for triplet 1s ns states of the helium atom. Comparison with near-exact results from Nakatsuji's free ICI method reveals that HF theory provides a simple route to accurate energies of these Rydberg states, especially for large n. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Bound D-states of helium atom under Debye screeningINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2007Sabyasachi Kar Abstract We have investigated the 1snd1,3D (3 , n , 7) state energies of helium atom embedded in weakly coupled plasma environments using the Rayleigh,Ritz variational method. The effect of the plasma environment is taken care of using a Debye screening model. A correlated wave function involving exponential expansion has been used to represent correlation between the charge particles. The bound 1snd1,3D (3 , n , 7) state energies of helium for various Debye lengths along with the excitation energies of few singlet and triplet states are reported. Our results are useful references to atomic physics, plasma physics, and astrophysics research communities. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Helium fine structure: Unsolved many-body-QED ProblemINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2006Ingvar LindgrenArticle first published online: 12 JUL 200 Abstract Theoretical and experimental results for the fine-structure separation of the lowest 3P state of the helium atom disagree significantly. The experiment is well checked and the disagreement is most likely due to deficiency in the theoretical evaluation, which is based upon power expansion of the Bethe-Salpeter equation. A new numerical technique is introduced for combining QED and electron-correlation calculations, which in the future might contribute to resolving the issue. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Radiative transitions of the helium atom in highly magnetized neutron star atmospheresMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008Z. Medin ABSTRACT Recent observations of thermally emitting isolated neutron stars revealed spectral features that could be interpreted as radiative transitions of He in a magnetized neutron star atmosphere. We present Hartree,Fock calculations of the polarization-dependent photoionization cross-sections of the He atom in strong magnetic fields ranging from 1012 to 1014 G. Convenient fitting formulae for the cross-sections are given along with the related oscillator strengths for various bound,bound transitions. The effects of finite nucleus mass on the radiative absorption cross-sections are examined using perturbation theory. [source] Development of ambient sampling chemi/chemical ion source with dielectric barrier dischargeJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2010Lee Chuin Chen Abstract The development of a new configuration of chemical ionization (CI)-based ion source is presented. The ambient air containing the gaseous sample is sniffed into an enclosed ionization chamber which is of sub-ambient pressure, and is subsequently mixed with metastable species in front of the ion inlet of the mass spectrometer. Metastable helium atoms (He*) are used in this study as the primary ionizing agents and are generated from a dielectric barrier discharge (DBD) source. The DBD is powered by an AC high-voltage supply and the configuration of the electrodes is in such a way that the generated plasma is confined within the discharge tube and is not extended into the ionization chamber. The construction of the ion source is simple, and volatile compounds released from the bulky sample can also be analyzed directly by approaching the sample to the sampling nozzle. When combined with heated nitrogen or other desorption methods, its application can also be extended to non-volatile compounds, and the consumption for helium can be kept minimum solely for maintaining the stable discharge and gas phase ionization. Applications to non-proximate sample analysis, direct determination of active ingredients in drug tablets and the detection of trace explosive such as hexamethylene triperoxide diamine are demonstrated. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||