Helium atomic spectrum

The atomic spectrum of singly ionized helium He+ with i = 4, 2 = 5, 6,. .. is known as the Pickering series. Calculate the energy differences, wave numbers, and wavelengths for the first three lines in this spectrum and for the series limit. 

The spectacular success of Bohr s theory was followed by a series of disappointments. Bohr s approach did not account for the emission spectra of atoms containing more than one electron, such as atoms of helium and lithium. Nor did it explain why extra lines appear in the hydrogen emission spectrum when a magnetic field is applied. Another problem arose with the discovery that electrons are wavelike How can the position of a wave be specified We cannot define the precise location of a wave because a wave extends in space. 

Helium was identified by its characteristic emission spectrum as a component of the sun before it was found on earth. The major sources of helium on earth are natural gas deposits, where helium was formed from the a-particle decay of radioactive elements. The a particle is a helium nucleus that can easily pick up electrons from the environment to form a helium atom. Although helium forms no compounds, it is an important substance that is used as a coolant, as a pressurizing gas for rocket fuels, as a diluent in the gases used for deep-sea diving and spaceship atmospheres, and as the gas in lighter-than-air airships (blimps). 

Evidence has been advanced8 that the neutral helium molecule which gives rise to the helium bands is formed from one normal and one excited helium atom. Excitation of one atom leaves an unpaired Is electron which can then interact with the pair of Is electrons of the other atom to form a three-electron bond. The outer electron will not contribute very much to the bond forces, and will occupy any one of a large number of approximately hydrogen-like states, giving rise to a roughly hydrogenlike spectrum. The small influence of the outer electron is shown by the variation of the equilibrium intemuclear distance within only the narrow limits 1.05-1.13 A. for all of the more than 25 known states of the helium molecule. 

Fig. 13.10 Sonoluminescence spectrum of potassium-atom emission from helium-saturated KC1 aqueous solution at 148 kHz. The spectrum shows slightly asymmetric broadening toward blue side, which is in contrast with the potassium line in argon-saturated solution...

The second source for which it has been claimed the detection of redshifted spectral lines is IE 1207.4-5209, a radio-quite compact star located in the center of the supernova remnant PSK 1209-51/52. IE 1207.4-5209 has been observed by the Chandra X-ray observatory. Two absorption features have been detected in the source spectrum and have been interpreted (Sanwal et al. 2002) as spectral lines associated with atomic transitions of once-ionized helium in the atmosphere of a strong magnetized (B 1.5 x 1014 G) compact star. This interpretation gives for the gravitational redshift at the star surface z = 0.12 -0.23 (Sanwal et al. 2002), which is reported in Fig. 3 and by the two dashed lines labeled z = 0.12 and z = 0.23. 

To conclude, it seems that the nature of the anharmonic coupling between a high frequency intramolecular mode and a thermally excited low frequency mode is understood. It turns out that the strength of the influence on the infrared spectrum critically depends on the values of (Oq, Sm and t. However, we have to wait for more experimental data on these low frequency modes, probably obtained with the helium atom scattering technique, bdbre we can make more definite conclusions. 

In ISS, like in SIMS, gas ions such as helium or neon are bombarded on the sample surface at a fixed angle of incident. The ISS spectrum normally consists of a single peak of backscattered inelastic ion intensity at an energy loss that is characteristic of the mass of surface atom. From the pattern of scattered ion yield versus the primary ion energy, information about elements present on the sample surface can be obtained at ppm level. 

The main aim of this paper is to review the CDW-EIS model used commonly in the decription of heavy particle collisions. A theoretical description of the CDW-EIS model is presented in section 2. In section 3 we discuss the suitablity of the CDW-EIS model to study the characteristics of ultra-low and low energy electrons ejected from fast heavy-ion helium, neon and argon atom collisions. There are some distinct characteristics based on two-centre electron emission that may be identified in this spectrum. This study also allows us to examine the dependence of the cross sections on the initial state wave function of multi-electron targets and as such is important in aiding our understanding of the ionization process. 

Lockyer s studies of the solar spectrum revealed to him that the sun is a miasma of chemical elements. Where did they come from In 1873 Lockyer developed the theory, later expounded in his Chemistry of the Sun (1887), that in the hottest (blue-white) stars the stellar matter is broken apart into the constituents of atoms themselves subatomieparticles, the protyle discussed by Dumas. Then, as the stars cooled, these particles combined to form regular elements - including some, like helium, not (then) known on Earth. 

In helium, the para-state is one group or system of terms in the spectrum of helium that is due to atoms in which the spin of the two electrons are opposing each other. Another group of spectral terms, the orthohelium terms, is given by those helium atoms whose two electrons have parallel spins. Because of the Pauli Exclusion Principle, a helium atom in its ground state must be in a para-state. 

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