Noble gas polarizability

Table 9.6 Electronic Polarizabilities for Selected Ions and Molecules in A3a. Atoms and Ions with Noble Gas Configurations 2 electrons He Li+ Be2+ B3+ C4+ 0.201 0.029 0.008 0.003 0.0013 ...

The van der Waals well depth e increases monotonically as the polarizability of the ground-state partner increase, whereas the location of the well, rm, remains roughly constant at about 6A. This is expected by analogy with the well-known alkali-noble-gas potentials,116-119 although the rm values are larger than for the alkali case, as shown in Table V. 

In the region of negligible overlap, the three-body interactions can be calculated, just like the two-body ones, from imaginary frequency polarizabilities. This has been done, for example, by Doran78 for interaction of triplets of noble-gas atoms. He gives the coefficients for dipole-dipole-dipole, dipole-dipole-quadrupole, dipole-quadru-pole-quadrupole, quadrupole-quadrupole-quadrupole, and dipole-dipolc-octupole terms. 

Depending on the type of interaction between an adsorbed particle and a solid state surface there are cases, where adsorption enthalpies can be calculated using empirical and semi-empirical relations. In the case of atoms with a noble-gas like ground-state configuration and of symmetrical molecules the binding energy (EB) to a solid surface can be calculated as a function of the polarizability (a), the ionization potential (IP), the distance (R) between the adsorbed atom or molecule and the surface, and the relative dielectric constants (e) (Method 9) [58-61] ... 

The heats of vaporization are measures of the work that must be done to overcome interatomic attractive forces. Since there are no ordinary electron-pair interactions between noble gas atoms, these weak forces (of the van der Waals or London type) are proportional to the polarizability and inversely proportional to the ionization enthalpies of the atoms they increase therefore as the size and diffuseness of the electron clouds increase. 

In addition to UV/visible flash photolysis and TRIR spectroscopy, other techniques have been used for the detection of transition metal-noble gas interactions in the gas phase. The interaction of noble gases with transition metal ions has been studied in detail. A series of cationic dimeric species, ML" " (M = V, Cr, Fe, Co, Ni L = Ar, Kr, or Xe), have been detected by mass-spectroscopic methods (55-58). It should be noted that noble gas cations L+ are isoelectronic with halogen atoms, therefore, this series of complexes is not entirely unexpected. The bond dissociation energies of these unstable complexes (Table IV) were determined either from the observed diabatic dissociation thresholds obtained from their visible photodissociation spectra or from the threshold energy for collision-induced dissociation. The bond energies are found to increase linearly with the polarizability of the noble gas. 

It would appear that since He is just bound, the heavier and more polarizable noble gas atoms also may be bound. Indications given above suggest that 0 ,... 

The noble gas configuration (d for metal ions is associated with high spherical symmetry and electron sheaths that are not readily deformed by electric fields that is, their polarizabilities are low, or, in more descriptive language, they are hard spheres. 

A chemical reaction between an atom (X = He, Li+, Be2+, B3+, C4+) in various electronic states and a proton to form an XH+ molecule has been mimicked by a collision between X and H+. Maximum hardness and minimum polarizability values characterize a favorable dynamical process. Since a system becomes more reactive on electronic excitation, it becomes softer and more polarizable. A proton being a hard acid would prefer the most to react with X in its ground state according to HSAB principle in a dynamical context, and the preference will gradually decrease with electronic excitation. This fact is corroborated in this QFDFT [17,47] study on protonation [64] through a decrease in the maximum hardness value and an increase in the minimum polarizability value on excitation. Reactivity of noble gas elements toward protonation increases as He < Ne < Ar < Kr < Xe. 

In Table 1, first and second ionization potentials, and I2, and dipole polarizabilities a of the noble gas elements and some first row elements are listed. The electron affinities of the noble gas elements are not shown, because they are essentially zero. This indicates that none of the noble gas elements accepts an electron from any other neutral atom or molecule. 

Table 1. First and second ionization potentials /, and /j (in eV) and static electric dipole polarizabilities a (in A ) for noble gas elements and first-row atoms...

Table 9 Calculated and Experimental Electric Polarizabilities of the Noble Gas Atoms (10 cm )...

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