124,654 research outputs found
Assignment of the S1-S0 Electronic Absorption Spectra of 1H-Benzotriazole and of 1,2,4-Triazolo[1,5-a]Pyrimidine as π*-π by Rotational Band Contour Analysis
No full textThe 000 bands in the S1-S0 electronic absorption systems of lH-benzotriazole at 286 nm and of 1,2,4-triazolo[l,5-a]pyrimidine at 315 nm have been analyzed by computer simulation of their rotational contours. The results have shown that the benzotriazole hand is an almost pure type-B band, while in the case of 1,2,4-triazolo[l,5-a] pyrimidine it is a pure type-A band, so each S1-S0 electronic system is assigned as Ã1A′(ππ*)-X̃1A′. In both of these molecules, the transition moment is in the molecular plane, almost parallel to the b-inertial axis in benzotriazole. while it is parallel to the a-inertial axis in 1,2,4-triazolo[1,5-a]pyrimidine. Since the S1-S0 transitions in the indole derivatives previously analyzed were shown to be π*-π, it seems likely that the nature of the S1-S0 electronic transition is the same in all the molecules of this kind. © 1993 Academic Press, Inc
Borgo Velino
No full textCenni sulla nascita e l'evoluzione del centro di Borgo Velino (RI). Notizie sulle principali opere del periodo barocco presenti in loco
Assignment of the 290-nm electronic band system of indazole [1,2-benzodiazole] as π* - π by rotational band contour analysis
No full textThe 000 band of the S1-S0 electronic absorption system of indazole at 290 nm has been analyzed, and the results of the computer simulation of its rotational contour have shown that this band is and A B hybrid with an intensity ratio A B = 1.22. The S1-S0 electronic system is assigned as A ̃1A′(ππ*)- X ̃1A′. The same result has already been reached for benzimidazole (E. Canéet al., J. Mol. Spectrosc.150, 222-228 (1991)), and other ring-condensed aza-aromatic compounds although the relative amount of the type B and A components is different in each band. The transition moment is in the molecular plane nearly equidistant from the a- and b-inertial axes (θ = ±42°). © 1992
Assignment of the 278-nm electronic band system of benzimidazole [1,3-benzodiazole] as π* - π by rotational band contour analysis
No full textThe 000 band of the 278-nm electronic band system of benzimidazole has been rotationally analyzed by computer simulation of its rotational contour. It has been shown to be an A B hybrid with an intensity ratio B A = 0.11. The S1-S0 electronic system is assigned as A ̃1A′(ππ*)- X ̃1A′. Since the same result has already been reached for other ring condensed aza-aromatic compounds, we conclude that the number and location of nitrogen atoms in these molecules do not change the nature of the S1-S0 transition. © 1991
Internal dynamics features in the free jet rotational spectrum of the acetaldehyde-Kr molecular complex
No full textThe structure and the dynamics of internal motions in the complex formed between acetaldehyde and Kr are studied by free jet absorption microwave spectroscopy performed in the range 60–78 GHz. The fourfold structure of each rotational line is evidence of the vibration-rotation coupling between the overall rotation of the complex, a tunneling motion of the Kr atom between two equivalent positions and the internal rotation of the methyl group in the acetaldehyde moiety. The four sets of transitions could be fitted with a coupled Hamiltonian which allows for the Coriolis interaction obtaining the energy separation between the vibrational energy levels related to the tunneling motion, while the observed splittings due to the methyl group internal rotation were analyzed independently with an appropriate model. The potential energy barriers for the tunneling motion and the internal rotation of the methyl group have been calculated and the interaction of the rare gas atom with the acetaldehyde moiety is reflected in the change of the V3 barrier to internal rotation in going from the molecule to the weakly bound complex
Microwave spectrum of benzimidazole
No full textThe microwave spectra of benzimidazole and of its N-D monodeuterated isotopic species, obtained at 120°C, show the full planarity of the molecule. Information on the lower energy vibrational excited states, and on the dipole moment have also been obtained. © 1992
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Microwave Spectra of Benzotriazole and Pyrimidinotriazole
No full textThe microwave spectra of 1H-benzotriazole and its N-D isotopomer and of 1,2,4-triazolo[1,5-a]pyrimidine have been investigated in a heated cell. Both molecules are planar. Their dipole moments have been measured. The rotational spectra of some vibrational satellites belonging to the butterfly and 1,3-twisting vibrations have also been assigned. © 1993 Academic Press, Inc
Pyridine-CF4: A Molecule with a Rotating Cap
No full textThe rotational spectrum of pyridine-CF4 has been investigated by molecular beam Fourier transform microwave spectroscopy in a supersonic expansion. The CF4 moiety is located as a cap over the pyridine nitrogen, and the two parts are freely rotating with respect to each other. For this reason, in a first approximation, in the m = 0 state only the pyridine ring is rotating along the a-axis, and the value of rotational constant A' is nearly the same of the constant A of isolated pyridine. The (NCCF4)-C-..., distance is 3.372(1) angstrom. The dissociation energy has been estimated, from the centrifugal distortion, to be ca. 10 kJ/mol
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
