1,721,202 research outputs found
Second harmonic generation by p-nitrophenol at water/air and water/heptane interfaces
No full textInterfacial second harmonic generation by p-nitrophenol at air/water and heptane/water interfaces has been investigated. The preliminary results indicate that the orientation of the p- nitrophenol is slightly different in the two cases. but the influence of the resonant enhancement on the two important components of the molecular hyperpolarisability (beta(zzz) and beta(zxx)) differs significantly in the two systems. The difference is attributed to the change in the absorption spectrum of p-nitrophenol in heptane and water
Rayleigh scattering of laser and synchrotron radiation from pulsed free jets of Ar-n and (N2O)(n) clusters
No full textRayleigh scattering has been used to determine the average size of clusters formed in pulsed free-jet expansions of Ar and N2O. The scaling behavior of the mean cluster size with backing pressure predicted by Hagena (Rev. Sci. Instrum. 1992, 63, 2374) and Buck and Krohne (J. Chenz. Phys. 1996, 105, 5408) has been shown to be applicable up to at least an average cluster size of 25 000. A similar scaling of the average cluster size with pressure was observed for both Ar and N2O. Competing photochemical and photophysical processes are shown to limit the use of short-wavelength radiation to observe Rayleigh scattering from the N2O clusters
Photolysis of HOCl at 248-nm in a supersonic molecular-beam - laser-induced fluorescence-spectra of OH
No full textPhotolysis of hobr and dobr at 266-nm - oh and od product-state distributions
No full textThe OH and OD rotational and vibrational product-state distributions have been recorded following the 266 nm photolysis of HOBr and DOBr, respectively, in a molecular beam. The photodissociation dynamics are similar to those observed for HOCl. The OH and OD distributions are rotationally cold and, for almost all of the states investigated, Gaussian in shape. Preferential population of the OH (or OD) 2PI3/2 spin- orbit state was observed, together with a strong preference for the PI(A') LAMBDA-doublet levels. The alignment, beta0(2)(02), tends towards the limiting value of -0.5 at the highest N levels that could be observed. In contrast to the photolysis of HOCl, about 10% of the OH fragment was observed in the first excited vibrational state, with a similar rotational distribution to the OH(v = 0) products. The OD product distributions from DOBr were found to be sensitive to the molecular-beam expansion conditions with a bimodal distribution obtained for the colder expansions. The photodissociation is consistent with excitation of a non-bonding electron to a sigma antibonding orbital which promotes rapid and direct bond fission via an upper state of A' symmetry
266 nm Photolysis of HOCl and DOCl: laser-excitation fluorescence detection of OH and OD
No full textFragment rotational population distributions for OH and OD were observed by laser-excitation fluorescence following the 266 nm photolysis in a free jet molecular beam of HOCl and DOCl, respectively. The photodissociation dynamics show a strong preference for the 2PI(A') OH or OD lambda doublet component in both spin-orbit states. The 2PI3/2 state is more populated than the 2PI1/2 State of OH. The distributions are consistent with photolysis via a repulsive excited state and the measured rotational alignment (-0.28) is compatible with an excited- state symmetry of A' for the dominant dissociation pathway. The high-J limiting value for the degree of electron alignment reaches the extreme value of - 1 for the 2PI1/2 state for both OH and OD, but falls short of this for the 2PI3/2 state, reaching only -0.7
Abinitio calculations on the ground and low-lying electronic states of the cl-3 radical - emission from cl-3
No full textBroad band, low level emission is observed in the region 370- 420 nm following the photolysis of Cl2 in a flow system at a pressure of 400 Torr in the presence of nitrogen buffer gas. It is suggested that the decay of an excited electronic state of the Cl3 radical is responsible for this emission. To support this claim a series of ab initio calculations on the Cl3 radical were performed with 6-31G and 6-31G* basis sets at the SCF and CI levels. The calculated C2v ground state agrees with the previous calculations but a lower minimum with an asymmetric structure, probably a van der Waals state, was also found. Ab initio SCF calculations on the ground state of Cl3- were also performed
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
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