Motion Of Electrons In Atoms Research Articles

Deformed Atoms and Collective Rotational Motion of Electrons

Collective rotational motion of electrons in the ground and low-lying excited states of Be-like ions is investigated by using the symmetry-violating mean field approach, the Peierls-Yoccoz projection method and the cranking model method. Characteristics of the deformation of atomic mean fields are discussed in comparison with those of nuclei. The present method gives an explicit intrinsic wave function, and thus provides a deeper insight into collective rotational motion of atomic electrons.

Analysis of covalent bonding by nonergodic Thomas–Fermi theory

It is proposed that covalent bonding can be understood as due to dynamical constraints on electronic motion in atoms which are partially relaxed upon molecule formation. The corresponding delocalization of electronic motion and settling of the electron density stabilizes the molecule. A preliminary implementation of the analysis is based on a form of Thomas–Fermi theory extended so as to account for dynamical constraints leading to a nonergodic population of phase space. Simple estimates for light atoms indicate that nonergodic effects in atoms correspond to large amounts of energy only partially released upon molecule formation due to a variety of antibonding mechanisms.

Looking at orbitals in the laboratory: The experimental investigation of molecular wavefunctions and binding energies by electron momentum spectroscopy

AbstractThe experimental technique of electron momentum spectroscopy (EMS) (i.e., binary (e, 2e) spectroscopy) is discussed together with typical examples of its applications over the past decade in the area of experimental quantum chemistry. Results interpreted within the framework of the plane wave impulse and the target Hartree—Fock approximations provide direct measurements of, spherically averaged, orbital electron momentum distributions. Results for a variety of atoms and small molecules are compared with calculations using a range of Fourier transformed SCF position space wavefunctions of varying sophistication. Measured momentum distributions (MD) provide a “direct” view of orbitals. In addition to offering a sensitive experimental diagnostic for semiempirical molecular wavefunctions, the MD's provide a chemically significant, additional experimental constraint to the usual variational optimization of wavefunctions. The measured MD's clearly reflect well known characteristics of various chemical and physical properties. It appears that EMS and momentum space chemistry offer the promise of supplementary perspectives and new vistas in quantum chemistry, as suggested by Coulson more than 40 years ago. Binding energy spectra in the inner valence region reveal, in many cases, a major breakdown of the simple MO model for ionization in accord with the predictions of many‐body calculations.Results are considered for atomic targets, including H and the noble gases. The measured momentum distribution for H2 is also compared with results from Compton scattering. Results for H2 and H are combined to provide a direct experimental assessment of the bond density in H2, which is compared with calculations. The behavior of the outer valence MD''s for small row two and row three hydride molecules such as H2O and H2S, NH3, HF, and HCl are consistent with well known differences in chemical and physical behavior such as ligand‐donor activity and hydrogen bonding. MD measurements for the outermost valence orbitals of HF, H2O and NH3 show significant differences from those calculated using even very high‐quality wavefunctions. Measurements of MD's for outer σg orbitals of small polyatomic molecules such as CO2, COS, CS2, and CF4 show clear evidence of mixed s and p character. It is apparent that EMS is a sensitive probe of details of electronic structure and electron motion in atoms and molecules.

Observing the motion of electrons in atoms and molecules

Abstract The dynamic electronic structure of atoms and molecules can be directly observed by means of the (e, 2e) reaction, which measures the distribution of energies and momenta of two electrons in coincidence after a knockout reaction initiated by an electron beam of known momentum incident on a molecular gas target. The molecular state for each event is identified by the electron separation energy. The recoil momentum for each event is known from the difference of measured initial and final momenta. It has been verified that values of this momentum are equal under suitable conditions to the momentum of the electron in the target immediately before knockout. Thus the spherically-averaged electron momentum distribution for each molecular orbital is measured. This is directly related to molecular orbitals calculated by the methods of quantum chemistry. Properties obtained by this method for different types of molecules are discussed.

A moiré pattern analogy to electron motion

The optical illusion produced by this pattern may help students better understand the motion of electrons in atoms.

The Use of Compton Scattering for the Study of Electron Velocities

A demonstration of the motion of electrons in atoms is described. The demonstration is provided by measuring the Doppler shift of gamma rays scattered by the moving electrons. Scattering materials of CH2, aluminum, brass, and lead were used; the scattered gamma ray spectra clearly show the differences in the electron velocities in these materials.