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Pagnoux-Ozherelyeva A.,CNRS Laboratory of Molecular and Thio-Organic Chemistry | Pannetier N.,CNRS Laboratory of Molecular and Thio-Organic Chemistry | Mbaye M.D.,CNRS Laboratory of Molecular and Thio-Organic Chemistry | Mbaye M.D.,University of Ziguinchor | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2012

An aminated series: A well-defined iron-catalyzed reductive amination reaction of aldehydes and ketones with aliphatic amines using molecular hydrogen is presented. Under mild conditions, good yields for a broad range of alkyl ketones as well as aldehydes were achieved. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Diatta S.,University of Ziguinchor | Diatta S.,Laboratory for Atmospheric and Oceanic Physics | Finkc A.H.,Karlsruhe Institute of Technology
International Journal of Climatology | Year: 2014

This paper revisits the strength and stationarity of linear statistical relationships between indices of monsoon rainfall derived from rain gauge data for three regions in tropical West Africa [West Sahel (WS), Central Sahel (CS), and Guinea Coast (GC)] and various indices describing remote variations in the ocean-atmosphere climate systems from 1921 to 2009. The results reveal that both the Atlantic Multi-decadal Oscillation (AMO) and the Atlantic Meridional Mode (AMM) show a positive linear correlation to Sahel rainfall. The percent variance explained (PVE) ranges from 10 to 25%. The correlation stems from periods longer than 8 years for AMO, but AMM does show a correlation on interannual time scales for WS that was absent in the 1970s and 1980s. The PVE by El Niño Southern Oscillation (ENSO) indices is, though statistically significant, on the order of 10% and found mainly on the interannual time scale. A strong and stable correlation with PVEs larger than 50% is found between the sea surface temperatures (SSTs) in the Atlantic 3 region (ATL3, 0°-20°W, 3°S-3°N) and the GC rainfall. On the other hand, the correlation between ATL3 and WS rainfall changed from significantly negative to significantly positive after the 1970s. The Eastern Mediterranean SSTs are found to be significantly related to CS rainfall, especially in recent years with PVEs between 36 and 47%. Multi-linear regression analyses reveal that the relative importance of the Indian Ocean is 42% in the optimal regression model. For the CS, this value is 37% for the Eastern Mediterranean SSTs and 70% in case of the GC using the ATL3 index. However, except for the GC, non-stationarities in the correlation between the climate state indexes and West African monsoon (WAM) rainfall suggest the need of the application of different regression models depending on the active 'teleconnection regime'. © 2014 Royal Meteorological Society.


Sakhoa I.,University of Ziguinchor
European Physical Journal D | Year: 2010

We present in this paper autoionizing energies of the 1P̊ states of H- and He belonging to the N = 3-13 hydrogenic thresholds. Calculations are performed for both intershell and intrashell resonances using the screening constant by unit nuclear charge (SCUNC) method in the framework of a semi-empirical procedure. The results obtained in this paper agree very well with available theoretical and experimental values. These agreements point out the possibility to use the SCUNC method in the study of other Rydbergtype series in doubly excited states of He-positive like ions. © EDP Sciences, Societá Italiana di Fisica, Springer-Verlag 2010.


Energy positions and quantum defects of the 4s24p4(1D2,1S0) n s, n d Rydberg series originating from the 4s24p52P3/20 ground state and from the 4s24p52P1/20metastable state of Kr+ are reported. Calculations are performed using the Screening Constant by Unit Nuclear Charge (SCUNC) method. The results obtained are in suitable agreement with recent experimental data from the combined ASTRID merged-beam set up and Fourier Transform Ion Cyclotron Resonance device (Bizau et al., 2011), ALS measurements (Hinojosa et al., 2012), and multi-channel R -matrix eigenphase derivative calculations (McLaughlin and Balance, 2012). In addition, analysis of the 4s24p4(1D2) n d and the 4s24p4(1S0) n d resonances is given via the SCUNC procedure. The excellent results obtained from our work point out that the SCUNC formalism may be used to confirm the results of the analysis from the standard quantum-defect expansion formulas. Eventual errors occurring in the analysis can then be automatically detected and corrected via the SCUNC procedure. © 2013 Elsevier Inc.


Sakho I.,University of Ziguinchor
Chinese Journal of Physics | Year: 2014

We present in this paper non-relativistic energies of the 1s2ns2S (n = 3-20) and 1s2np 2P (n = 2-20) excited states of the lithium-like ions using the screening constant by unit nuclear charge method. Calculations are performed up to Z = 20. In addition, high precision results for the fine structure splitting of the 1s2np 2P (n = 3, 4, and 5) levels of Z = 3-20 including quantum electrodynamics (QED) corrections are obtained, taking into account the solution of the Dirac relativistic equation of the hydrogen-like systems with the effective nuclear charge Z* = Z(1 - β), β being the screening constant by unit nuclear charge. It is shown that QED corrections are very significant for large Z systems, and then they should be included in any calculation for obtaining more accurate results. The present data agree very well with the experimental values from NIST and with various calculations. © 2014 The physical society of the republic of china.


Sakho I.,University of Ziguinchor
Chinese Journal of Physics | Year: 2013

We report in this paper on the ENn energy resonances of the doubly excited 1P° states of H- and He below the N = 4-10 threshold of H and He+, applying the modified orbital atomic theory in the framework of a semi-empirical procedure. The calculated energy levels are specified in terms of the supermultiplet classification scheme based on the new notations N(K, T)A n and N(ν)A n in the framework of the rovibrator model for the autoionizing states considered. Comparison of the N 〈r-1 12〉n radial expectation values of H- and He indicates that the angular quantum number K is effectively related to -〈cosθ12〉, with θ12 being the angle between the position vectors of the two electrons. In addition, comparison of the radial expectation values of H- and He shows that, for both intrashell and intershell N(K, T)A n, 1P° states, it is the Coulomb force which causes the differences observed in the photoabsorption spectra of H- and He. All the results presented in this work compared well with the available literature values. © 2013 The Physical Society Of The Republic Of China.


The 2(1,0)+ n 1S e,2(1,0)- nS e, 2 (1,0) -1P0, 2(1,0) + n 3P0, 2(0,1) + n, 2 (0,1)+ 1 3P0, 2(1,0)+1 nDe and 2(1,0)-3 nDe intershell autoionizing states of the helium-like ions are studied using the screening constant by unit nuclear charge (SCUNC) method in the framework of a semi-empirical procedure. The results up to Z = 10 compared well to the available experimental and theoretical literature data. In addition, the possibility to apply the SCUNC method in the calculations of energy resonances of heavy-Z helium-like ions is demonstrated in the present work where energy positions for some low-lying 2sns 1S e, 2snp 1P0 and 2pnp 1D e (n≥ autoionizing states with 11 ≥Z ≥28 are tabulated and comparison with double sums over the complete hydrogen spectrum calculations [A.I. Ivanov, I.U. Safronova, Opt. Spectrosc. 75, 506 (1993)] is made. A host of results presented in this paper may be useful guideline for future experimental and theoretical investigations in high-lying 1,3Se, g 1,3S eP0 and 1,3De De doubly excited states as well as in lower than in heavy-Z two-electron systems. © 2010 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.


Sakho I.,University of Ziguinchor
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

We report calculations of accurate high-lying energy resonances of the 4s24p2 (1D2)nd and 4s24p2 (1S0)nd Rydberg series originating from the 4s24p32P1/2,3/20 and 4s24p32D3/2,5/20 metastable states of Se+. The calculations are performed using the screening constant by unit nuclear charge (SCUNC) method up to n=40. The results obtained are compared with the first theoretical R-matrix calculations and with recent ALS measurements. Analysis of the present results is achieved in the framework of the standard quantum-defect theory and of the SCUNC procedure by calculating the effective charge. It is shown that the SCUNC method reproduces excellently the ALS results up to n=25. Our predicted data up to n=40 may be of great importance for the atomic physics community in connection with the modeling of plasma and astrophysical systems. © 2012 American Physical Society.


Sakho I.,University of Ziguinchor
Atomic Data and Nuclear Data Tables | Year: 2016

Photoabsorption of the 1s22s22p6 (1S0) ground state of Ne-like ions is presented in this paper. Resonance energies and width of the 2s2p6np1P1 series of Ne and Ne-like Na+, Mg2+, Al3+, Si4+, P5+, S6+, and Cl7+ ions are reported. Wavelengths of the 2s22p6 (1S0) →2s22p5(2P3/2,1/2)nd transitions in neon-like Na+ ion and of the 2s22p6(1S0)→2s2p6np1P1 transitions in Ne and in Ne-like Na+, Mg2+, Al3+, Si4+, P5+, S6+, and Cl7+ ions are tabulated. Analysis of the resonances investigated is done in the framework of the LS, jj and JK coupling schemes. All the calculations are made using the Screening constant by unit nuclear charge (SCUNC) formalism. Very good agreement is found between the SCUNC results and various experimental and theoretical literature values and new data for the Ne-like Si4+, P5+, S6+, and Cl7+ ions are listed. © 2015 Elsevier Inc.


Sakho I.,University of Ziguinchor
Radiation Physics and Chemistry | Year: 2011

The Screening Constant by Unit Nuclear Charge (SCUNC) method is used to study (2pns) 1,3P° and (2pnd) 1,3P° autoionizing states of the beryllium atom. Energy positions are reported up to n=20. In addition, resonance widths of the (2pns) 1P° states also presented. The current results compared very well to available theoretical and experimental literature values up to n=15. The accurate data presented in this work may be of interest for future experimental and theoretical studies in the photoabsorption spectrum of Be. © 2011 Elsevier Ltd.

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