Neon-helium interaction

Figure 11. Radial distribution functions for the water-water (ideal solution), helium-water, and neon-water interactions at infinite dilution at =1.0 and p, = 1.5.

Gases such as helium, neon and argon are so unreactive that we call them the inert gases. They form no chemical compounds, and their only interactions are of the London dispersion force type. They cannot form hydrogen bonds, since they are not able to bond with hydrogen and are not electronegative. 

Table 3.1 lists measured spectral moments of rare gas mixtures at various temperatures. (We note that absorption in helium-neon mixtures has been measured recently [253]. This mixture absorbs very weakly so that pressures of 1500 bar had to be used. Under these conditions, one would expect significant many-body interactions the measurement almost certainly does not represent binary spectra.) For easy reference below, we note that the precision of the data quoted in the Table is not at all uniform. Accurate values of the moments require good absorption measurements over the whole translational frequency band, from zero to the highest frequencies where radiation is absorbed. Such data are, however, difficult to obtain. Good measurements of the absorption coefficient a(v) require ratios of transmitted to incident intensities, /(v)//o, that are significantly smaller than unity and, at the same time, of the order of unity, i.e., not too small. Since in the far infrared the lengths of absorption paths are limited to a few meters and gas densities are limited to obtain purely... 

A common result of all the experiments is that most molecules quench the alkali resonance radiation very effectively with total cross sections ranging from 10 A2 to over 200 A2. However, if the molecule BC is replaced by a rare-gas atom, the quenching cross sections become very small at thermal energies. They are probably below 10 2 A2 for quenching by helium, neon, argon, krypton, and xenon.55 The latter result is easily understood in terms of Massey s adiabatic criterion.67 If Ar is a characteristic interaction range, v the impact velocity, and AE the energy difference between initial and final electronic states E(3p) and E(3s), respectively, then we must have a Massey parameter... 

Atoms of a single element may combine into one molecule, and atoms of different elements may combine to form compounds, which are also molecules. The latter usually happens when elements having incomplete electron shells interact. Atoms of different elements can attain full and stable electron shells by transferring or sharing electrons with each other. When this happens, these atoms are then held closely together by chemical bonds. Elements whose atoms have full electron shells, like helium and neon, tend to be the most stable and least likely to form compounds with other elements. 

L opez Cacheiro J, Fernandez B, Marchesan D, Coriani S, Hattig C, Rizzo A (2004) Coupled cluster calculations of the ground state potential and interaction induced electric properties of the mixed dimers of helium, neon and argon. Mol Phys 102 101-110... 

In particular, the potential functions for helium adsorbed on argon and for neon, argon, and xenon adsorbed on xenOn are shown here, and the theoretically predicted adsorption properties are compared with experiment, wherever possible. us (r ) for a Lennard-Jones atom interacting with a crystalline solid is given by the equation ... 

There are two ways that atoms can interact to attain noble-gas configurations. Sometimes atoms attain noble-gas configurations by transferring electrons from one atom to another. For example, lithium has one electron more than the helium configuration, and fluorine has one electron less than the neon configuration. Lithium easily loses its valence electron, and fluorine easily gains one ... 

The necessity of immobilisation for many of the above-mentioned technologies can significantly limit their application. Recently free-solution, label-free molecular interactions were investigated with back-scattering interferometry (BSI) in an optical train composed of a helium-neon laser, a microfluidic channel and a position sensor.56 Molecular binding interactions between proteins, ions and protein as well as small molecules and protein could be monitored without labelling or immobilising any of the interaction partners. 

Figure 7 Experimental signal recorded for photolyzed MbCO. Fe-ligand vibrations dominate the cluster of modes observed in the 230-270 cm region. The clearly resolved frequency separation between the in-plane Fe-N, yr frequencies at 251 and 267 cm reflects the asymmetric interactions with the histidine ligand. The Fe-histidine stretching frequency appears at 234cm L Data were recorded under continuous illumination by a 15 mW helium neon laser with k = 633 nm. The temperature of a sensor mounted in the sapphire sample block was 15 K...

The validity of either of these classical methods for calculating the induced moment contribution to Be can be judged by noting that both predict positive values of Be for atomic gases, in disagreement with the negative results reported for helium and neon. Comparison with ab initio calculations leaves little doubt that the inalnlity of clasacal methods to deal with short-range interactions caused by electron ovo-lap is responsiUe for the discrepancy. 

Induced polarizabilities differ from zero for a variety of reasons. A most important influence is the deviation of the local electric field from the externally applied laser field if another polarized atom or molecule is in close proximity. The classical dipole-induced dipole (DID) model considers the interacting pair as point dipoles [135, 136] and leads to separation-dependent invariants of the incremental polarizabilities [51, 62, 87, 115]. For the more highly polarizable particles, the DID anisotropy model is fairly accurate. Even for the less polarizable atoms such as helium and neon, at most separations of interest, the DID component of the anisotropy is known to be... 

The helium pair polarizability increment has been studied extensively [19, 29, 39, 41, 48, 56, 57, 63]. We mention in particular the most recent work by Dacre [48], which includes a careful review of previous results. Systems such as H-H in the and states may be considered as tractable examples representative of various types of real collisional pairs [6,28,54, 55,66,74,85, 144, 145, 147]. Elaborate self-consistent field (SCF) calculations, supplemented by configuration interaction (Cl) corrections are also known for the neon diatom [50]. For atom pairs with more electrons, attempts have been made to correct the SCF data in some empirical fashion for Cl effects [47, 49]. Ab initio studies of molecular systems, such as H2-H2 and N2-N2 have been communicated [16, 18]. 

Quantum calculations of spectral profiles based on Eqn. (3) are known isotropic interaction is commonly assumed. Such quantum calculations account for detailed balance in exact ways and consider not only the free-state to free-state transitions of binary complexes but also the bound-free and bound-bound transitions involving bound van der Waals pairs that are an inseparable part of the CILS spectra. These bound-free and bound-bound components can be quite significant, especially at the lower temperatures and for massive systems [266, 302, 328] see also related work on dimer spectra [262, 263], and the review papers on CILS lineshapes [227, 231, 271]. Lineshape calculations are useful for the detailed comparison of the fundamental theory with spectroscopic measurements. For helium pairs, a close agreement between the fundamental theory and the recent measurements is now observed similarly for the neon pair [45]. 

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