Argon compounds
Computational ab initio methods used have included CCSD(T), MP2 (Møller–Plesset perturbation theory of the second order), CIS and CISD.
More powerful computers since the 1990s have made this kind of in silico study much more popular, being much less risky and simpler than an actual experiment.
[1] Argonium is formed when H2+ reacts with Ar atoms:[1] and it is also produced from Ar+ ions produced by cosmic rays and X-rays from neutral argon: When ArH+ encounters an electron, dissociative recombination can occur, but it is extremely slow for lower energy electrons, allowing ArH+ to survive for a much longer time than many other similar protonated cations.
When a higher-energy-level ArH* emits a photon and reaches the ground state, the atoms are too close to each other, and they repel and break up.
These Rydberg molecules can be considered as a protonated argon core, surrounded by an electron in one of many possible higher energy states.
[30] Ar(N2)+2 is produced by a supersonic expansion of a 10:1 mixture of argon with nitrogen through a nozzle, which is impacted by an electron beam.
These ions were formed by firing a green laser at a boron target in a gaseous mixture of helium, argon and nitrous oxide.
Experimentally the molecule is made from a low-pressure argon gas with 0.1% carbon dioxide, irradiated by a 150 V electron beam.
The known molecules include AgAr, Ag2Ar, NaAr, KAr, MgAr, CaAr, SrAr, ZnAr, CdAr, HgAr, SiAr,[37] InAr, CAr,[38] GeAr,[39] SnAr,[40] and BAr.
The widely used argon fluoride laser makes use of the ArF* excimer to produce strong ultraviolet radiation at 192 nm.
It is the surface energy that maintains an icosahedral shape, but for larger clusters internal pressure will attract the atoms into an fcc arrangement.
[60] ArBH was produced from boron monohydride (BH) which in turn was created from diborane by way of an ultraviolet 193 nm laser.
[63] Other polyatomic van der Waals compounds of argon, include those of fluorobenzene,[64] formyl radical (ArHCO),[65] 7-azaindole,[66] glyoxal,[67] sodium chloride (ArNaCl),[68] ArHCl,[69] and cyclopentanone.
[70] Argon dissolved in water causes the pH to rise to 8.0,[82] apparently by reducing the number of oxygen atoms available to bind protons.
[92] This is shorter than the sum of atomic radii of U and Ar of 3.25 Å, but considerably longer than a normal covalent bond to uranium.
[93] When xenon is included in the solid argon matrix up to a few percent, additional van der Waals molecules are formed: CUO·Ar3Xe, CUO·Ar2Xe2, CUO·ArXe3 and CUO·Xe4.
The advantage of liquid noble gases is that the medium is completely transparent to infrared radiation, which is needed to study the bond vibration in the solute.
[5] Attempts have been made to study carbonyl–argon adducts in the gas phase, but the interaction appears to be too weak to observe a spectrum.
[113] In the case of transition metal monoxides, ScO, TiO and VO do not form a molecule with one argon atom.
Computationally predicted shapes for these molecular ions are linear for CuCO+Ar, slightly bent T-shaped for Cu(CO)2+Ar and a trigonal pyramid with argon at the top and a flat star like copper tricarbonyl forming the base.
[165] Boroxyl ring cationic complexes with argon [ArB3O4]+, [ArB3O5]+, [ArB4O6]+ and [ArB5O7]+ were prepared via a laser vaporization at cryogenic temperatures and investigated by infrared gas phase spectroscopy.
[3] They were the first large stable gas phase complexes that feature strong dative bonding between argon and boron.
So the positive second charge on the metal atom should move to the argon, ionizing it, and then forming a highly repulsive molecule that undergoes a Coulomb explosion.
However these molecules appear to be kinetically stable, and to transfer the charge to an argon atom, they have to pass through a higher energy state.
C70·Ar has argon in octahedral sites and has the rock salt structure, with cubic crystals in which the lattice parameter is 15.001 Å.
The C70 ellipsoidal balls rotate freely in the solid, they are not locked into position by extra argon atoms filling the holes.
Argon atoms and oxygen molecules are similar in size, so that a greater range of miscibility occurs compared to other gas mixtures.
With more oxygen between 5.5 and 7 GPa, a cubic Pm3n structure exists, but under higher pressure it changes to a I42d space group form.
Argon infused TON zeolite (Ar-TON) is more compressible than Ne-TON as the unoccupied pores become elliptical under increased pressure.
HCCNgCN and HCCNgNC (Ng = Ar, Kr, Xe) are likewise computed to be stable, but experimental searches for them have failed.
