Rare gas complexes

It is useful to view optical absorption and emission processes in such a system in terms of transitions between distinct vibrational levels of the ground and excited electronic states of a metal atom-rare gas complex or quasi-molecule. Since the vibrational motions of the complex are coupled with the bulk lattice vibrations, a complicated pattern of closely spaced vibrational levels is involved and this results in the appearance of a smooth, structureless absorption profile (25). Thus the homogeneous width of the absorption band arises from a coupling between the electronic states of the metal atom and the host lattice vibrations, which is induced by the differences between the guest-host... 

The most extensive potential obtained so far with experimental confirmation is that of Le Roy and Van Kranendonk for the Hj — rare gas complexes 134). These systems have been found to be very amenable to an adiabatic model in which there is an effective X—Hj potential for each vibrational-rotational state of (c.f. the Born Oppenheimer approximation of a vibrational potential for each electronic state). The situation for Ar—Hj is shown in Fig. 14, and it appears that although the levels with = 1) are in the dissociation continuum they nevertheless are quasi bound and give spectroscopically sharp lines. 

The van der Waals attraction between Br and I2 is estimated to be 400 cm-1 by analogy with halogen/rare gas complexes (Bieler and Janda 1990 Bieler et al. 1991). This ensures that photodissociation of the HBr moiety cannot produce Br + I2 except via quenching of Br or the unlikely instance in which the hydrogen is trapped efficiently between the heavv particles. With the Br atom unable to escape from the I2 because of the Br-I2 van der Waals attraction, the system is ensured of an essentially unity quantum yield. 

Reactions related to equation (6) are probably the most intensively studied in the whole field of organometallic chemistry. Ultrafast kinetics have given evidence for the formation of intermediates such as alkane and rare gas complexes in this system. ... 

Fig. 1.19. Scheme of the experimental setup for infrared multiphoton ionization or dissociation of clusters or of metal clusters-rare gas complexes. The charged and neutral clusters are directly emitted from the laser vaporization/supersonic expansion source. The beam passes a skimmer and is subsequently crossed by the tightly focused beam of the FELIX. At some time after the FELIX pulse is over, the time-of-flight mass spectrometer acceleration plates are pulsed to high voltage, and a mass spectrum is recorded in a standard reflectron setup. Also schematically depicted is the particular pulse structure of the FELIX light [126,127]... 

Rotational reorientation of frans-stilbene in alkane solution at room temperature occurs in the 10 to 30-ps time domain [347]. Rare-gas complexes with trons-stilbene were studied by purely rotational coherence spectroscopy [51,364]. Moreover, the decay kinetics of excited trans-stil-bene-cyclodextrin complexes were examined [366], It is worth mentioning that great progress has also been made in high-resolution spectroscopy [52, 369-372], Resonance coherent Raman spectroscopy showed a large enhancement of the electronic hyperpolarizability of t with respect to ground state trons-stilbene [374]. Vibrational motions were observed with ps transient Raman spectroscopy [375]. 

Sb-H bonds, 489 Sb-halogen bonds, 489 Se-H bonds, 451 Se-halogen bonds, 451 Si-Br bonds, 465 Si-Cl bonds, 464 Si-F bonds, 464 Si-H bonds, 455 Si-1 bonds, 465 Sn-Br bonds, 475-476 Sn-Cl bonds, 475 Sn-F bonds, 475 Sn-H bonds, 473 Sn-1 bonds, 476 Te-H bonds, 453 Te-halogen bonds, 453 Rare gas complexes anions, 1452 cations, 1446-1452 neutrals, diatomic, 1429-1436 polyatomic, 1436-1446 Rb-contarnmg species neutrals, 557-559 Rb clusters, 559-562 Rb clusters, 562-563 Re-containing species neutrals,796-799 Re clusters, 799-801 Re clusters, 801 Rh-contarnmg species neutrals, 882-892 Rh clusters, 892-894 Ru-containing species neutrals, 840-848 Ru clusters, 849-851... 

McKellar A R W and Welsh H L 1971 Anisotropic intermolecular force effects in spectra of H2- and D2-rare gas complexes J. Chem. Phys. 55 595-609... 

Fig. 5. The optical absorption spectrum and the electronic structure of Vs" ", (a) Experimental data, where a photodissociation action spectrum of a rare-gas complex, Vs+Ar, was measured by observing a photofragment, Vs+. (b) Density-functional calculation of the spectrum for the most stable isomer illustrated in the inset. The bars show oscillator strengths the solid line a spectral profile, (c) Density-of-states profiles of the majority or and the minority-spin electrons obtained by the density-functional calculation. The shadows indicate occupied electronic levels. The vanadium pentamer ion. Vs" ", was shown to be in the spin triplet state with a trigonal bipyramid structure, where the average bond length was 2.4...

The spectroscopic studies of silver atom van der Waals complexes, Ag—Ar, Ag—Kr, Ag—Xe, presented in this section supplement the earlier investigations of silver dimer-rare gas complexes " and extend also previous studies of the laser-induced fluorescence of the Ag—Ar system . New resonant two-photon ionization spectra of Ag Ar, Ag Kr, Ag Xe complexes have been presented and the positions of bands (as well as their assignments to 11 band systems) have been tabulated as follows ... 

Bergman and coworkers have applied liquid Xe as a useful solvent for C—H activation. For the Cp IrLH2 system, it allowed study of methane, as well as of more exotic alkanes, such as cubane and adamantane in the latter case the 2-adamantyliridium hydride was formed on irradiation" ". In addition, time-resolved IR spectroscopic studies were carried out in Xe and Kr which led to the proposal that alkane complexes are in equilibrium with rare gas complexes in this system (equation 14). The alkane complex is the last observed precursor before the alkyl hydride is formed". ... 

Sta Stangassinger, A., Knight, A.M., Duncan, M.A. Photoionization spectroscopy of Ga-rare gas complexes, J. Chem. Phys. 108 (1998) 5733-5741. 

A comparison of the experimental and theoretical results compiled to date on the open-shell OH-Ar complex with earlier work on hydrogen halide-rare gas systems indicates that OH-Ar in its ground electronic state is much like these closed-shell systems. Upon vibrational excitation of the OH bond, OH-Ar exhibits a long vibrational predissociation lifetime, an increased well depth, and a slight lengthening of the vdW bond. These are much the same effects observed for the hydrogen halide-rare gas complexes. The ab initio intermolecular potential for OH-Ar is also similar to those determined for ArHF and ArHCl. The similarities between OH-Ar and ArHCl or ArHF are not surprising in that the vibrational frequency, rotational constants, and dipole moments of the OH radical are comparable to those of the HCl and HF molecules. 

Weber et al have investigated van der Waals vibrational transitions in T Ar and other tetrazine-rare gas complexes. They observed that (i) the frequencies of these transitions in the cluster T X (X = Ar, Kr, Xe) fit fairly well in with harmonic or near harmonic progressions and (ii) the relative intensities of corresponding transitions of stretch vibrational modes are sensibly uncoupled, unless the vibrational mixing in the three different clusters would be very similar. 

Halberstadt et al. have discussed the rotational state distribution of Cl produced by vibrational predissociation of chlorine-rare gas complexes. 

For complexes between a given aromatic molecule and different rare gas atoms, the red shift increases from neon to xenon. A linear correlation exists between this spectral shift and the rare gas atom polarizability as already obtained by other groups for other aromatic-Rg complexes, e.g. the aniline-rare gas complexes /7/ confirming the linear dependence, with the rare gas polarizability a, of the vdW interaction of a mainly dispersive nature. 

In this manuscript, we report on the direct observation of such electronic state changing processes in the dissociation of a diatom-rare gas complex, namely NelQ in the P ( 2 = 1) ion-pair state. 

The application of these techniques is considerably enhanced by the introduction of sarrple-seeded supersonic jets. Gas-phase spectra are obtained at effective temperatures close to the absolute zero and the problem of Boltzmarm congestion" is effectively overcome. Besides making the analysis of previously hopelessly congested spectra tractable it has revealed a new family of weakly-bound van der Waals dimers or clusters. Some of the analyses are hmited to general conclusions, as e g. the distinction between end-on and sideways-on orientation of diatomic iodine in a benzene-iodine complex. Such data are not included in the present compilation. Other analyses, however, yield accurate intemuclear distances as in the benzene-rare gas complexes. 

Gerber, I. C., 8c Angyan, J. G. (2007). London dispersion forces by range-separated hybrid density functional with second order perturbational corrections The case of rare gas complexes. Journal of Chemical Physics, 126, 044103. 

---