Far infrared (terahertz) spectroscopy of a series of polycyclic aromatic hydrocarbons and application to structure interpretation of asphaltenes and related compounds

Analytical Gas Sensing in the Terahertz Spectral Range

Exploiting the terahertz (THz) part of the electromagnetic spectrum is attracting attention in various scientific and applied disciplines worldwide. THz technology has also revealed its potential as an effective tool for gas analysis in astronomy, biomedicine and chemical analysis. Recently, it has also become important in environmental applications for monitoring hazardous and toxic gases in the atmosphere. This paper gives an overview of THz gas detection analytical methods for environmental and biomedical applications, starting with a brief introduction to THz technology and an explanation of the interaction of THz radiation with gaseous species and the atmosphere. The review focuses on several gaseous species and groups of air pollutants that have been or can be analysed by THz spectrometry. The review concludes that different but complementary THz detection methods allow unique detection, identification and quantification of gaseous and particulate air pollutants with high selectivity, specificity and sensitivity. THz detection methods also allow further technological improvements and open new application possibilities.

Far Infrared spectrum of naphthalene in the 5-15 THz range: Experimental and theoretical study

The Fourier Transform Infrared technique was employed to measure the terahertz spectrum of naphthalene at room temperature. Naphthalene exhibited six absorption bands in the 5-15 THz range, two of which have not been previously reported. The additional bands appeared at 5.80 and 6.37 THz. Density Functional Theory modeling with PBE0 and TPSSh functionals gave vibrational modes which matched well with the experimental bands despite the slight shifts in energies. The TPSSh functional was found to perform slightly better than the PBEO functional. Comparison of the naphthalene spectrum with the spectrum of terra preta suggested the existence of cyclic hydrocarbons in terra preta.

Low-energy vibrational spectra of flexible diphenyl molecules: biphenyl, diphenylmethane, bibenzyl and 2-, 3- and 4-phenyltoluene

Gas phase spectra of six bi-phenyl molecules are reported allowing an accurate determination of their active low-frequency vibrational modes.