Metal vapor spectroscopy

In its more recent phase of development, the multidisciplinary nature of metal-vapor cryochemistry is becoming evident with, for example, chemical physicists attempting to explain subtle, spectroscopic phenomena associated with matrix-entrapped, metal atomic species (75-77). A clear display of renewed physics interest in the field may be seen from a glance at the proceedings of the International Conference of Matrix Isolation Spectroscopy (Ber. Bunsenges. Phys. Chem., January, 1978). In addition, matrix reactions are providing unique, syn-... 

From this brief exposure to the pervasive character of metal-vapor cryochemistry and matrix-isolation spectroscopy, it is clear that a field of multidisciplinary concern is surveyed. However, in this review, we shall focus on those accomplishments of greatest interest to the inorganic community in general, while pointing out, where applicable, the relevance of the results to other branches of chemistry and physics. 

Figure 1. Schematic illustration of the laser-vaporization supersonic cluster source. Just before the peak of an intense He pulse from the nozzle (at left), a weakly focused laser pulse strikes from the rotating metal rod. The hot metal vapor sputtered from the surface is swept down the condensation channel in dense He, where cluster formation occurs through nucleation. The gas pulse expands into vacuum, with a skinned portion to serve as a collimated cluster bean. The deflection magnet is used to measure magnetic properties, while the final chaiber at right is for measurement of the cluster distribution by laser photoionization time-of-flight mass spectroscopy.

The (C Me ) Sm(THF) metal vapor product provided the first opportunity ta see if Smdl) complexes (y =3.5—3.8 Ufi) could be characterized by H NMR spectroscopy (24). Fortunately, the paramagnetism doesn t cause large shifting and broadening of the resonances and hence samarium provides the only Ln(III)/Ln(II) couple in which both partners are NMR accessible. Once the existence and identity of (C Mej- SmdHF) was known, a solution synthesis was developed from KC Me and Sml THF) (44). This system is the preferred preparative route and also provides another soluble organosamarium(II) complex, [(C Me )Sm(THF)2(u-I)]2, under appropriate conditions. This is another xample of how solution studies subsequently catch up to the research targets often identified first in metal vapor reactions. 

HeCd Metal vapor 0.441, 0.325 0.05-0.1 Light shows, spectroscopy... 

The far quasistatically broadened wings of the Na D transition give important contributions to the emission and absorption spectrum of a high-pressure sodium discharge. We report experimental and theoretical spectra and discuss in particular the Na2 triplet satellite at 551.5 nm and the Na2 singlet satellite at 805 nm. Extension of this type of spectroscopy to other alkali metal vapors is discussed. 

Recently in our laboratory we have initiated a program to study the photoabsorption processes of metal vapors throughout the UV and EUV region. Our research interests are (1) to obtain the absolute cross section measurement of atomic and molecular metal vapors, (2) to study the photoionization processes of molecular metal species, and (3) to study the photodissociation processes of molecular metal ions. Several experimental methods such as the heat-pipe absorption spectroscopy, photoionization mass spectroscopy, and electron-ion coincidence technique, will be used in the study. This report summarizes our first experiment using heat-pipe absorption spectroscopy. 

Another route to trapping small Fe and Co particles within the supercages of faujasite zeolites is the metal vapor solution condensation ( metal atom solvate ) method, used by Nazar and Ozin 148). When characterized by Fe Mossbauer and ferromagnetic resonance spectroscopies, Fe particles in the size range of 5-12 A are located in the zeolite supercage and its 12-member ring entrance. In using these Fe -NaY or Co -NaY catalysts for... 

Figure 7. Conversion of standard cryogenic matrix isolation equipment for use in microscale, liquid phase metal vapor synthesis and spectroscopy. Continued on next page.

The alkaline earth metals form a host of unique monovalent free radicals. Most of these molecules can be formed by the laser-driven chemical reactions of metal vapors with a wide variety of organic and inorganic molecules. This photochemical production of new molecules has led to an extensive gas-phase inorganic chemistry and spectroscopy of alkaline earth derivatives. In recent years, the Broida oven source has been displaced by the pulsed molecular beam spectrometer. The chemical dynamics and photochemistry of these new molecules are still at a very early stage of investigation. 

Fig. 1. Schematic representation of vacuum furnace closed-cycle helium refrigeration system used for metal vapor microsolution optical spectroscopy, as well as conventional metal vapor-matrix isolation experiments. (A) NaCl or Suprasil optical window, horizontal configuration (B) stainless steel vacuum shroud (C) NaCl or Suprasil optical viewing ports (D) cajon-rubber septum, liquid or solution injection port (E) gas deposition ports (F) vacuum furnace quartz crystal microbalance assembly. With the optical window in a fixed horizontal configuration, liquid or solution sample injection onto the window at any desired temperature in the range 12-300 K is performed in position 1A, metal deposition is conducted in position IB, and optical spectra are recorded in position 1C see Procedure).

In hollow cathodes the cathode material can be sputtered by ion bombardment in the discharge. The metal vapor, consisting of atoms and ions, can be investigated by optogalvanic spectroscopy. Figure 1.43b illustrates a section of the optogalvanic spectrum of aluminum, copper, and iron atoms, and ions A1+, Fe , measured simultaneously in two hollow cathodes irradiated with a tunable pulsed dye laser [120]. 

Enhancement of absorption bands in the IR spectra of ultrathin films in the presence of discontinnons (islandlike) nnder- and ovemanolayers of Ag and An was discovered by Hartstein et al. [356] in the early 1980s. Although these researchers believed that they observed an increase in the vCH band intensities for p-nitro-benzoic acid (p-NBA), benzoic acid, and 4-pyridine-COOH films, it was recently shown [350] that the spectra reported are in actual fact due to fully saturated hydrocarbons (possibly vacuum pump oil). In any case, this discovery has stimulated various research activities and led to the development of surface-enhanced IR absorption (SEIRA) spectroscopy. To date, the SEIRA phenomenon has been exploited in chemical [357] and biochemical IR sensors (see [357-360] and literature therein), in studying electrode-electrolyte interfaces [171, 361-365], and in LB films and SAMs [364, 366-370]. Other metals that demonstrate this effect are In [371] and Cu, Pd, Sn, and Pt [372-375]. The metal films can be prepared by conventional metal deposition procedures such as condensation of small amounts of metal vapor on the substrate, spin coating of a colloidal solution, electrochemical [388], or reactive deposition [299] (see also Section 4.10.2). 

Two separate samples of NasCgo were prepared by direct reaction of Ceo with sodium metal vapor, and subjected to different annealing times of 10 16 days. C and Na solid-state NMR, along with elemental analysis, powder XRD and Raman spectroscopy, were used to characterise both samples. Na and C solid-state NMR spectra of the two samples are significantly different, suggesting a relationship between annealing times and the final structure of the alkali fulleride. Na VTMAS NMR experiments reveal the existence of two or three distinct Na species and reversible temperature-dependent diffusion of sodium ions between octahedral and tetrahedral interstitial sites. C MAS NMR experiments are used to identify resonances corresponding to free Ceo and fulleride species. ... 

R Indralingham, JB Simeonsson, GA Petrucci, BW Smith, JD Winefordner. Raman spectroscopy with metal vapor filters. Anal Chem 64 964-967, 1992. 

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