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91.
Jeyaraman Chandrasekhar Prem Kishore Mehrotra Sankaran Subramanian Periakaruppan T. Manoharan 《Theoretical chemistry accounts》1979,53(3):293-296
Siegbahn's potential model as extended by Ellison et al. is used with density matrix elements calculated by the NDDO/2 procedure, to correlate the K-shell binding energy shifts of C, N and O atoms in a few molecules containing only the first-row atoms. The correlation is not superior to that obtained with the CNDO/2 method when only the monopole term is retained in calculating the Madelung potential energy. However, the results are in excellent agreement with experiment when the two-parameters model including the dipole and quadrupole terms is used. 相似文献
92.
93.
Rampur S. Viswanath Philip J. Miller Charles A. Cody 《Journal of Physics and Chemistry of Solids》1979,40(3):223-229
IR transmission, near-normal IR reflection and polarized Raman spectra of single crystals of selenious acid (H2SeO3) have been obtained at temperatures between 77°K and 335°K. The observed bands in the O-H stretching region have been assigned to two types of O-H….O bonds in the crystal structure. The spectral results appear to rule out correlation field splittings, intramolecular coupling, or Fermi resonance as explanations for the observed splitting. A proposed model based on intermolecular coupling of O-H….O vibrations to explain the splitting of the O-H stretching region is given. 相似文献
94.
The adsorption of oxygen on W(100) single crystal surfaces is studied by Auger electron spectroscopy (AES), flash desorption, low-energy electron diffraction (LEED) and retarding field work function measurements with the aim of obtaining a better understanding of the adsorption kinetics and of the structures of the adsorbed layer. The AES results reveal step-wise changes of the sticking coefficients in the coverage range 0 to 1, and activated adsorption at higher coverages. Upon room temperature adsorption a series of complex LEED patterns is observed. In layers adsorbed at 1050 K and cooled to room temperature, the well-known p(2 × 1) structure is the first ordered structure observed. This structure shows a reversible order-disorder transition between 700 K and 1000 K and is characterized by a work function which is lower than that of the clean surface. Heating room temperature adsorbates changes their structure irreversibly. At temperatures below 750 K some new structures are observed. Combining the results obtained in this study with other published work leads to a considerable revision of the previously accepted model of the adsorption of oxygen on W(100). 相似文献
95.
The co-adsorption of Cu on O2 and a W{100}surface is studied by Auger electron spectroscopy (AES), thermal desorption (TD), low energy electron diffraction (LEED) and by work function change (δø) measurements. It is shown that the presence of Cu on the surface initially decreases sO, the sticking coefficient of O2. For longer oxygen exposures and for higher adsorption temperatures, θO reaches values larger than those on the clean surface for the same O2 exposure. Except at the highest θO values and temperatures, the sticcking coefficient for copper, sCu, is unity and is independent of the oxygen coverage θO in the range studied (0 ? θO ? 2). Co-adsorption at room temperatures does not produce any long range order while co-adsorption at elevated temperature leads to the ordered structures (1 × 1), p(2 × 1), p(2 × 2) and c(2 × 2). The saturation coverage of the two dimensional co-adsorbate at 800 K is given by the relation . The work function is a complicated function of θO and θCu and is determined predominantly by the temperature at which oxygen is adsorbed. At high temperatures the sequence of adsorption has no influence, in contrast to the room temperature behavior. 相似文献
96.
Yamada K Murugesan R Devasahayam N Cook JA Mitchell JB Subramanian S Krishna MC 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,154(2):287-297
The performance of two electron paramagnetic resonance (EPR) spectrometers/imagers, one configured in pulsed mode and the other in continuous wave (CW) mode, at an operating frequency of 300 MHz is compared. Using the same resonator (except for altered Q-factors), identical samples and filling factors in the two techniques have been evaluated for their potentials and limitations for in vivo spectroscopic and imaging applications. The assessment is based on metrics such as sensitivity, spatial and temporal resolution, field of view, image artifacts, viable spin probes, and subjects of study. The spectrometer dead time limits the pulsed technique to samples with long phase memories (>275 ns). Nevertheless, for viable narrow-line spin probes, the pulsed technique offers better sensitivity and temporal resolution. The CW technique, on the other hand, does not restrict the choice at spin probes. In addition, the phase-sensitive narrow-band detection of the CW technique gives artifact-free images even for large objects. Selected examples illustrating the performance of the CW and pulsed techniques are presented to put the capabilities of the two techniques in perspective. 相似文献
97.
The present study deals with the experimental investigations of static pressure and mean velocity fields obtained as a result
of the interaction of two plane turbulent jets at impingement angles of α equal to 30° and 45°, with an additional central
jet in a confined space. The investigation is carried out for the velocity ratios of U
c/U
o=1.0, 2.0 and 3.0, where U
c and U
o are the velocities in the central plane at the exit of the central jet and the outer jets, respectively. The introduction
of the central jet alters the various recirculation zones present in the flow field for all the cases considered above. Also,
the change in the velocity ratio U
c/U
o has a significant effect on the pressure and mean velocity flow fields. Flow visualisation results are presented which give
a better physical insight into the flow field considered.
Received: 26 July 1999/Accepted: 14 February 2000 相似文献
98.
Salim Saranya Sankaran Radhika Cheriya Mukkolakkal Afsina Abdulla Gopinathan Anilkumar 《Journal of heterocyclic chemistry》2021,58(8):1570-1580
The synthesis of heterocyclic compounds has been a hot topic for several decades. Synthetic organic chemists are always in search of new methodologies which are greener for the synthesis of heterocyclic compounds. The ultrasound-assisted reactions have contributed much to this field. This review focuses on the impact of sonochemistry in the synthesis of heterocyclic compounds and covers the literature from 2009 to 2020. 相似文献
99.
The Ramanujan Journal - The 15 primes 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 41, 47, 59, 71 are called the supersingular primes: they occur in several contexts in number theory and also,... 相似文献
100.
Anusree Viswanath Kuttatheyil Marcel Handke Jens Bergmann Dr. Daniel Lässig Dr. Jörg Lincke Prof. Dr. Jürgen Haase Dr. Marko Bertmer Prof. Dr. Harald Krautscheid 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1118-1124
Spectroscopic techniques are a powerful tool for structure determination, especially if single‐crystal material is unavailable. 113Cd solid‐state NMR is easy to measure and is a highly sensitive probe because the coordination number, the nature of coordinating groups, and the geometry around the metal ion is reflected by the isotropic chemical shift and the chemical‐shift anisotropy. Here, a detailed investigation of a series of 27 cadmium coordination polymers by 113Cd solid‐state NMR is reported. The results obtained demonstrate that 113Cd NMR is a very sensitive tool to characterize the cadmium environment, also in non‐single‐crystal materials. Furthermore, this method allows the observation of guest‐induced phase transitions supporting understanding of the structural flexibility of coordination frameworks. 相似文献