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The infrared spectra of crystalline thiophene have been reinvestigated. New data on the four phases have been obtained and conditions for obtaining them are described. The structures of the two phases registered at 77 K are discussed.

The infrared and Raman spectra of 2,2′-bifurane in the liquid and solid state have been measured between 4000 and 50 cm −1 . Infrared spectra in polarized light have been obtained at 85°K on oriented polycrystalline samples. The observation of two different crystal faces allowed to identify all the Davidov components. Splitting of the normal modes was also observed for most of the Raman active fundamentals. The molecules have been found to be trans planar in the crystal and to assume different conformations in the liquid. The data obtained from the crystal spectra are consistent with an orthorhombic factor group with four molecules located at C i sites. An almost complete assignment of the fundamentals is also reported.

Polarized spectra of the title compound were recorded and the assignment of the most relevant bands is discussed. Particular attention is paid to the B u type band at 1680 cm −1 which is not accounted for in the factor group analysis.

Per la prima volta il metodo degli operatori lineari multipli viene fondato su una conveniente rappresentazione analitica delle funzioni di due o piu variabili, che rende agevole la risoluzione del problema diCauchy per l'equazione delle onde (oltre che l'integrazione indefinita delle equazioni di tipo ellittico lineari alle derivate parziali del 2o ordine a coefficienti costanti).

The infrared spectrum of isothiazole vapour has been measured between 4000 and 400 cm−1 under high resolution. The assignment of the fundamental modes, based on the rotational envelope of the vapour bands and on the previous assignments for isoxazole and isoxazole-d3 is discussed.

The infra-red spectra of pyrimidine- d 0 and - d 4 have been measured between 4000 and 300 cm −1 in gas, liquid and solid phases. Since the analysis of the rotational band envelopes alone was not sufficient for a definite assignment, useful information was gained from the interpretation of the crystal spectra in polarized light of both isotopic species. A new vibrational assignment is presented which differs from that given previously by L ord et al. for the six fundamentals ν 6 a , ν 19 a , ν 6 b , ν 18 b , ν 19 b , ν 4 . The experimental evidence for the new assignment is discussed in detail.

The vibrational spectrum of (2,2')paracyclophane has been measured between 4000 and 50 cm −1 . The assignment of the ir -active fundamentals was essentially based on the crystal spectra in polarized light of two different kinds of polycrystalline samples. The oriented gas model holds strictly and no deviations occur between the experimental and the theoretical dichroism. Through a correlation with the Raman spectrum of the crystal, is was possible to separate b 2u and b 3u molecular species which are degenerate ( E u ) in the crystal.

Si esamina il regime termico negli strati superiori della crosta terrestre in alcuni casi elementari di discontinuita del materiale, nonche nell'ipotesi di una superficie esterna sagomata a gradino, traendone deduzioni atte a facilitare l'interpretazione ed a valorizzare i dati geotermici.

Infra-red and Raman spectra of 5,5′-bis-isoxazole-h4 and -d4 in the crystal state and in solution have been measured and the dichroism of the infra-red bands in polycrystalline samples has been determined. The data obtained are consistent with a trans planar structure in the crystal. In the liquid state and in solution, the molecule exists in a single distorted configuration, as shown by the spectra at different temperature and by the value of the dipole moment. An almost complete assignment of the fundamentals in the crystal has been obtained.

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E contenuto nel n. 1 del testo. The subject of this paper is explained in the first lines of it.

Non-bonded interaction and PPP calculations using various refinements were accomplished on cis- and trans-conformations of 5,5′-bis-isoxazole, to study the problem of internal rotation of this molecule. For comparison purposes, 2,2′-bipyridyl and biphenyl were also treated by the same procedure. Results are discussed together with those of previous researches on biphenyl. With the simple PPP approximations, values of ΔEcis-trans of –30 and +5.5 kcal/mol were found for bis-isoxazole and bipyridyl, respectively, while the introduction of “penetration” integrals gave values of +10 and +20 kcal/mol, respectively. The strong dependence of these results upon the different approximations indicates that this approach, which had been satisfactory for biphenyl, cannot describe more complex problems arising in the study of internal rotation.

Scopo principale di questa Nota e di indicare un procedimento per la valutazione di un gruppo di operatori funzionali che si presentano nell'Elettrodinamica e in altri rami della Fisica, e che si possono ricondurre al tipo $$\left( {\frac{{m + l\Delta }}{{g + k\Delta }}} \right)^n ,$$ dove Δ=ϖ/ϖt, mentrem, l, g, k sono quantita positive, indipendenti dat, edn e una costante reale.

The infrared spectra of pyrazine-d0, cis pyrazine-d2 and pyrazine-d4 have been measured between 4000 and 400 cm−1. The spectra have been obtained in the vapour and solid states. The dichroic behaviour of the bands has been measured on polycrystalline fully oriented samples. The vibrational assignment of the three isotopic species id discussed on the basis of the rotational band envelopes, of the polarization measurements and of the product rule. All infrared active modes are assigned and from the infrared spectrum of cis pyrazine-d2 evidence is obtained for the choice of infrared inactive modes of pyrazine.

The infra-red and Raman spectra of oxazole and thiazole have been measured in different conditions in order to get definite evidence for a complete assignment of the normal vibrations of these ring compounds. The vibrational assignment of oxazole and thiazole is then discussed on the basis of the collected experimental results. The correlation with the normal modes of similar ring molecules is substantiated and discussed.

Infra-red spectra of 1,2,5-oxadiazole have been measured between 4000 and 400 cm −1 in the vapour, liquid, and solid phases. The Raman spectrum of the liquid with polarization measurements has also been obtained. A vibrational assignment of the fundamental frequencies has been made on the basis of the rotational envelope analysis of the infra-red vapour bands and of the polarization of the Raman lines.

Infrared spectra of pyridine‐H5 and pyridine‐D5 in the solid state were measured between 4000 and 200 cm− 1. Frequencies and polarization of fundamental absorptions were established for oriented thin films of freshly crystallized samples. Behavior of the bands in polarized light aided in clarifying several assignments. The multiplicity of several of the bands was accounted for by close‐lying overtones and combinations. Some of the components of ν26 are due to the existence of appreciable amounts of 13C isotope species clearly observable in a nitrogen matrix at 5°K. For pyridine‐D5 a phase transition was clearly observable after several hours of annealing of thin films at about − 60°C, but similar transformation could not be induced in normal pyridine. The infrared crystal data are consistent with an orthorombic factor group established by x‐ray analysis with no molecule on any symmetry element of the crystal. Raman spectra of liquid and solid pyridines are also reported.