Hydrogen spectral features

Despite its success in reproducing the hydrogen atom spectmm, the Bolir model of the atom rapidly encountered difficulties. Advances in the resolution obtained in spectroscopic experiments had shown that the spectral features of the hydrogen atom are actually composed of several closely spaced lines these are not accounted for by quantum jumps between Bolir s allowed orbits. However, by modifying the Bolir model to... 

In Figure 12a (Pd Pt = 1 2) and 12b (Pd Pt = 1 1), only the spectral feature of CO adsorbed on the Pt atoms, i.e., a strong band at 2068 cm and a very weak broad band at around 1880 cm was observed, while that derived from CO adsorbed on Pd atoms at 1941 cm is completely absent, which proved that the Pd-core has been completely covered by a Pt-shell. Recently we also characterized Au-core/Pd-shell bimetallic nanoparticles by the CO-IR [144]. Reduction of two different precious metal ions by refluxing in ethanol/ water in the presence of poly(A-vinyl-2-pyrrolidone) (PVP) gave a colloidal dispersion of core/shell structured bimetallic nanoparticles. In the case of Pd and Au ions, the bimetallic nanoparticles with a Au-core/Pd-shell structure are usually produced. In contrast, it is difficult to prepare bimetallic nanoparticles with the inverted core/shell, i.e., Pd-core/Au-shell structure. A sacrificial hydrogen strategy is useful to construct the inverted core/shell structure, where the colloidal dispersions of Pd cores are treated with hydrogen and then the solution of the second element, Au ions, is slowly... 

Table 6.6 Infrared Spectral Features Associated with Hydrogen Bonding. ...

Chemiluminescence is observed from several different emitting species, depending on the analyte and reaction conditions. Vibrational overtone bands of HF in the wavelength region of =500-900 nm are observed under nearly all conditions and are often the dominant spectral feature, the (3,0), (4,0) (5,1), and (6,2) bands being the most intense, while for some reaction conditions emissions from levels up to v = 8 are observed [63], It is likely that hydrogen atoms are produced in the reaction and form vibrationally excited HF in the reaction reported by Mann et al. [62] ... 

A quick impression of a star s metallicity can often be derived from inspection -either qualitative or quantitative - of strong spectral features such as the CN band A, 4215 in giants or comparison of hydrogen and Ca+ K-line (A 3933) intensities, which has been particularly useful in the discovery of extremely metal-deficient stars (Beers, Preston Shectman 1992). Numerical comparisons of digital spectra with low signalinoise ratio can also be carried out for this purpose (Carney et al. 1987). 

Fig. 3.17. Spectrum of the central region of an SO galaxy, NGC 3384, showing hydrogen, magnesium and iron spectral features used in the Lick system. The resolution is 3.1 A ( 75kms 1), compared to a line-of-sight velocity dispersion 140kms 1. After Fisher, Franx and Illingworth (1996). Courtesy Garth Illingworth.

As pointed out before, the IR/UV double resonance spectra of the complexes between F and the enantiomers of 2-amino-1-propanol (alaninol) exhibit spectral features due to structures involving not only the expected intermolecular hydrogen bonding (either OH- - -O or OH- - -N), but also extensive intramolecular OH- - -N and OH- - -TThydrogen bonding. Similar intramolecular interactions are present in the isomeric [C/j-M/ r], [C/j-M/ s], and [C/j-Mss] adducts as well. 

When it became possible to obtain the spectrum of one of these objects in 1937, it was obvious that they looked like nothing yet known. All supernovas discovered in subsequent years displayed a remarkable uniformity, both in intensity and in behaviour. This observation led Zwicky to suggest that they might be used as standard candles to calibrate distance across the cosmos. But then, in 1940, a supernova with a completely different spectrum was discovered. It soon became clear that there were at least two classes of supernova, distinguished by their spectral features. It was the presence or absence of the Balmer lines of hydrogen near the maximum of the light curve that provided this classification. 

As in the case for adsorbed but-l-ene on Pt/Si02, the broad absorption at 1600 cm-1 in Fig. 25A is attributed to the presence of chemisorbed bridged hydrogen. It intensifies on heating up to above 473 K, and this would be consistent with additional surface hydrogen from thermal decomposition of the hydrocarbon species. At the same time, the alkyl absorptions become weaker and broader while a broad absorption from v=CH and/or v=CH2 grows to become the strongest spectral feature at 573 K. 

The term unidentified infrared emission is used to refer to the long-known emission features of interstellar dusts in the spectral region from just over 3,000 cm-1 to below 800 cm-1 (Gillett et al. 1973). These features comprise sharp IR bands at 2,920,1,610, and 880 cm-1, as well as a broader envelope near 1,300 cm-1. In addition, a recurrent mode at 3,050 cm-1, a weak mode near 1,450 cm-1, and a shoulder near 1,150 cm-1 are observed. These spectral features can all be attributed to vibrational modes of hydrogenated carbon species, as summarized in Table 2.1. The chemical structure of these species remains the subject of debate. Furthermore, a number of carbon-rich astronomical objects reveal an emission feature in the far-IR at 490 cm-1, of unclear attribution (Kwok et al. 1989). 

Fig. 2.1 HREEL spectra of C60 multilayer films shown as a function of increasing hydrogen exposure. The primary electron beam energy is 6 eV and the sample temperature is -150°C. (a) no hydrogen exposure, FWHM = 36.5 cm-1 (b) a 45 L hydrogen exposure, FWHM = 34.8 cm-1 (c) a 180 L hydrogen exposure, FWHM = 40.4 cm-1 and (d) a 1,000 L hydrogen exposure, FWHM = 60.4 cm-1. Spectral features labeled for comparison with Table 2.1 (Reproduced by permission of the AAS from Stoldt et al. 2001).

Mixtures of fulleranes produced by hydrogenation of solid C60 films under atomic H flux have revealed spectral features that bear striking similarity to those observed in the diffuse interstellar medium, both in the far IR and in the UV spectral windows. Of course, one must be cautious not to overextend the interpretation of laboratory data, for a number of reasons firstly, because electron spectroscopy, the experimental technique used in these studies, differs in several important aspects from the spectroscopic methods employed in observational astronomy, and secondly, because of the specifics of specimen preparation and environmental conditions. In this regard, there is a need to explore the stability of fulleranes to energetic and corpuscular radiation (Cataldo et al. 2009). Nonetheless, our findings lend support to the suggestion of fulleranes as candidates for unidentified emission and absorption features of interstellar and circumstellar media. Whether or not they exist in sufficient abundance is still unclear however, their spectral features make them undoubtedly an ideal model system for laboratory studies of these fascinating astrophysical phenomena. 

Besides, the review could conditionally be divided in accord with another criterion, (a) In Sections III-V and VII we discuss so-called unspecific interactions, which take place in a local-order structure of various polar liquids, (b) In Sections VI-IX we also consider specific interactions [16]. These are directly determined by the hydrogen bonds in water, are reflected in the band centered at 200 cm-1, which is termed here the R-band, and is characterized by some spectral features in the submillimeter wavelength range (from 10 to 100 cm-1). Note that sometimes in the literature the R-band is termed the translational band, since the peak frequency of this band does not depend on the moment of inertia I of a water molecule. 

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