[en] High signal-to-noise ratio 5-8 μm spectra of four sources embedded in molecular clouds are presented. All four sources show evidence for the presence of absorption features. The shape of these features changes, however, dramatically from source to source. They range from two relatively narrow bands at 6.0 and 6.8 μm in W33A to a broad, shallow feature, which extends from about 5.2 to 7.8 μm and shows some structure, in Mon R2-IRS2, BN, and NGC 2264

[en] A classification scheme for QSO absorption line spectra is described which ascribes the origin of the lines to at least four mechanisms: (A) Explosive ejection of material at speeds up to 0.1 c. (B) Absorption by highly ionized material moving in a rich cluster in which the QSO is embedded. (C-1) Cosmologically distant intervening material with 'normal' abundances, probably associated with large galactic halos. (C-2) Cosmologically distant intervening material consisting of primordial uncondensed gas. Examples of each type of spectra are given and their ionization and other spectral characteristics discussed. The similarity between the development of novae spectra and a possible evolutionary sequence of the explosive ejecta of type A is striking and suggestive. Several difficulties and unsolved problems involving this scheme are noted. Finally, the author speculates on the interpretation of two interesting objects (PKS 0237-23 and the 'twin quasars' 0957+56A,B) in the context of this scheme. (Auth.)

No abstract available

No abstract available

[en] The optical spectra of PbMoO₄:Er³+ single crystals at 77 and 300K are investigated, the optical transitions of Er³+ ions in the crystals are identified and the experimental scheme of Stark splitting of Er³+ ions lowest multiplets are obtained. 6 refs

[en] In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L₃ and the Pb M₅ edges of the methylammonium lead iodide (MAPbI₃) hybrid inorganic-organic perovskite and its binary phase PbI₂. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI₃ are essentially given by its inorganic component, with negligible influence from the organic groups. Furthermore, the theoretical analysis complementing experimental observations provides the conceptual insights required for a full characterization of this complex material.

No abstract available

No abstract available

[en] The A and B bands of calcium hydride are identified at high dispersion in the SC star, UY Cen. In the SC stars, the B band is largely responsible for the lambda 6379 absorption noted by Rybski (1973). CaH is also present in the CS star TT Cen, but may not be responsible for the lambda 6379 absorption in WZ Cas. (U.S.)

[en] At present, many researchers are exploring biological tissue inspection using terahertz time-domain spectroscopy (THz-TDS) techniques. In this study, based on a modified hard modeling factor analysis method, terahertz spectral unmixing was applied to investigate the relationships between the absorption spectra in THz-TDS and certain biomarkers of gastric cancer in order to systematically identify gastric cancer. A probability distribution and box plot were used to extract the distinctive peaks that indicate carcinogenesis, and the corresponding weight distributions were used to discriminate the tissue types. The results of this work indicate that terahertz techniques have the potential to detect different levels of cancer, including benign tumors and polyps. (paper)