1,721,338 research outputs found
Spin-forbidden transitions in the vicinity of the 2 (1)Pi(u)<- X(1)Sigma(+)(g) band system of Rb(2)
No full textWe have investigated the Rb(2) 475 nm system by resonance enhanced two-photon ionization spectroscopy in a pulsed molecular beam. Strong extra bands accompanying the 2 (1)Pi(u) nu' = 5 - 8 <- X (1)Sigma(+)(g) nu '' = 0 bands were newly observed. Rotational analysis of the main and extra bands reveals that the 2 (1)Pi(u) nu' = 5 - 8 levels are significantly perturbed, mainly by the 3 (3)Sigma(+)(u)(1(u)) state and also by the 2 (3)Pi(u)(1(u)) state. For the major perturber, 3 (3)Sigma(+)(u)(1(u)), the intensity borrowing has been found to be facilitated by the 2 (3)Pi(+)(u)(1(u)) potential energy curve crossing near 21100 cm(-1). For the vibronic-band intensities of the 2 (3)Pi(u)(1(u)) nu' <- X (1)Sigma(+)(g) nu '' = 0 transitions observed in this spectral region, intensity borrowing was most effective when the 2 (3)Pi(u)(1(u)) levels were close to the 3 (3)Sigma(+)(u)(1(u)) levels. A deperturbation fit for the perturbing bands has provided the 2 (1)Pi(u)-3 (3)Sigma(+)(u)(1(u)) coupling constants
Photodissociation and Laser Spectroscopy of alkali metal dimers in a very cold molecular beam
No full textConformational study of tyramine and its water clusters by laser spectroscopy
No full textTyramine and its monohydrated clusters have been investigated by several laser spectroscopic methods in a pulsed molecular beam. The conformational structures and their effects on hydration have been revealed by resonant two-photon ionization (R2PI), UV-UV ion-dip, and ab initio calculations. UV rotational band contour spectra of the S-1 <- S-0 origin bands enabled determination of ethylamine side chain conformations for all seven stable conformers of tyramine. When coexpanding tyramine with a mixture of Ar and water vapor, we have found two kinds of conformational effects on hydration. One is sensitive to conformation of the ethylamine chain and the other to the orientation of the OH group, particularly in the most stable pair of conformers. UV-UV ion-dip spectra detected seven stable conformers of the monohydrated clusters, of which hydrogen-bonding structures, spectral shifts, and origin band intensity distributions are well explained by considering tyramine as a hybrid of phenylethylamine (PEA) and phenol. Monohydration of the most stable gauche conformer pair (cis and trans) of tyramine leads to more detailed conformational assignments regarding the orientation of the phenolic OH group. Cyclic hydrogen-bonding linkage formed in the monohydrated cluster pair is found to be sensitive to the orientation of the phenolic OH group. One of the cluster pair, in which tyramine has the gauche-cis conformation, is more stabilized by the cyclic hydrogen bonding and its origin band intensity becomes stronger than that of the other
Observation of ultraviolet rotational band contours of the DNA base adenine: Determination of the transition moment
No full textWe report the first observation and analysis of rotational band contours of the jet-cooled DNA base adenine for three vibronic bands at 36 062, 36 105, and 36 248 cm(-1). The lowest n pi* and pi pi* states have been labeled with their excited-state vibronic symmetry, and a strong pi pi*-n pi* vibronic coupling via an out-of-plane vibrational mode has been revealed. The rotational band contours have been recorded by resonant two-photon ionization (R2PI) and analyzed by a genetic algorithm (GA) based fit to obtain the optimum band parameters. The vibronic band at 36 062 cm(-1) shows dominant c-type character with transition dipole moment (TDM) components mu(2)(a):mu(2)(b):mu(2)(c)=0.09: 0.17:0.74 and those at 36 105 and 36 248 cm(-1) show abc-hybrid character with predominantly in-plane TDM components. The band at 36 062 cm-1 has been assigned as the n ->pi* transition, and the 36 105 cm(-1) band as the pi ->pi* transition by the symmetry analysis. The band at 36 248 cm(-1) provides evidence of the strong pi pi*-n pi* vibronic coupling via an out-of-plane vibrational mode
Parallel and coupled perpendicular transitions of RbCs 640 nm system: Mass-resolved resonance enhanced two-photon ionization in a cold molecular beam
No full textWe have investigated the RbCs 640 run system by mass-resolved resonance enhanced two-photon ionization in a cold molecular beam. Very complex vibronic structures were observed between 15420 and 15990 cm(-1). The parallel transitions of 2 (3)Pi(0) nu' = 4-20 <- X (1)Sigma(+) nu '' = 0 were identified by rotationally resolved spectra. Molecular constants and a Rydberg-Klein-Rees potential energy curve of the 2 (3)Pi(0) state were determined. The regular vibrational spacing of the parallel transition indicated that the 2 (3)Pi(0) state is not significantly perturbed by nearby excited electronic states. The complexity of the observed vibronic structures has been attributed to the coupled perpendicular transitions of 2 (1)Pi , 2 (3)Pi(1) , and 3 Sigma (3)Sigma(+)(1)nu '' = 0. For the perpendicular bands observed in the lower-energy spectral region between 15420 and 15630 cm(-1) where the onsets of the 2 (3)Pi(1) and 3 (3)Sigma(+)(1) <- X (1)Sigma(+) transitions are located, the upper electronic states and the vibrational quantum numbers were assigned. Perturbations of 2 (3)Pi(1) and 3 3 Sigma(+)(1) and 2 (1)Pi-3 (3)Sigma(+)(1) have been identified by the observed level shifts
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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