Effect of polarization on population transfer in H2 by stimulated Raman transition with partially overlapping laser pulses

Polarization effects on population transfer by stimulated Raman transition using overlapping time dependent pump and Stokes laser pulses from the ground X ¹Σ _g ^/+ (v _g=0, J _g=1) level of H₂ to the final X ¹Σ _g ^/+ (v _f=1, J _f=1) level via the intermediate B ¹Σ _u ^/+ (v _i=14, J _i=0,2), C ¹Π _u ^/+ (v _i=3, J _i=2) and C ¹Π _u ^/− (v _i=3, J _i=1) levels have been theoretically investigated by applying the density matrix formalism. We have studied in detail the dependence of the population transfer on time delay between two pulses for the cases of on-resonance excitations considering linear parallel and same-sense circular polarizations of the fields. The pump and Stokes fields are taken as having Gaussian pulse shapes with peak intensities I _P ^/0 (I _S ^/0 )=2 × 10⁶ and 1 × 10⁷ W/cm². Density matrix equations have been solved for each value of the magnetic quantum number M _g(0, ±1) of the initial ground level taking into account the M _g dependence of the Rabi frequencies. M _g — averaged population transfer to the final level has also been calculated. For resonance excitations to the B(14, 0) or C(3, 1) levels, appreciable population transfer is achieved for intuitive pulse order for some particular values of M _g and M _i (magnetic quantum number of the resonant intermediate level) depending on the nature of polarizations. The calculated values of M _g — averaged population transfer for the two cases of polarizations show that for on-resonance excitation to the B(14, 0) or the C(3, 1) level, linear parallel polarization of the laser fields yield more transfer efficiency whereas for resonance excitation to the B(14, 2) level, larger population transfer results from the same-sense circular polarizations. For resonance excitation to the C(3, 2) level, M _g — averaged population is found to be almost polarization independent. The calculations for the six-level H₂ system reveal some interesting features of polarization effects on the population transfer efficiency.     

Ab initio calculations and molecular dynamics simulation of H2 adsorption on CN3Be3+ cluster

Hydrogen adsorption properties of the CN₃Be₃⁺ cluster have been studied using density functional theory and MP2 method with a 6–31++G** basis set. Five hydrogen molecules get adsorbed on the CN₃Be₃⁺ cluster with a hydrogen storage capacity of 10.98 wt%. Adsorption of three H₂ molecules on one of the three Be atoms in a cluster is reported for the first time. It is due to the more positive charge on this Be atom than the remaining two. The average value for H₂ adsorption energy in CN₃Be₃⁺ (5H₂) complexes is 0.41 (0.43) eV/H₂ at MP2 (wB97XD) level, which fits well within the ideal range. Adsorption energy from electronic structure calculations plays an important role in retaining the number of H₂ molecules on a cluster during atom-centered density matrix propagation (ADMP) molecular dynamics (MD) simulations. According to ADMP-MD simulations, out of five H₂ adsorbed molecules on CN₃Be₃⁺, four and two H₂ molecules remain absorbed on CN₃Be₃⁺ cluster at 275 K and 350 K, respectively, during the simulation.

     

THE SINGULARLY PERTURBED NONLOCAL REACTION DIFFUSION SYSTEM

In this paper the singularly perturbed initial boundary value problems for the nonlocal reaction diffusion system are considered. Unsing the iteration method and the comparison theorem, the existence, uniqueness and its asymptotic behavior of solution for the problem are studied.     

Linkage Determination of Linear Oligosaccharides by MSn (n > 2) Collision-Induced Dissociation of Z1 Ions in the Negative Ion Mode

Obtaining unambiguous linkage information between sugars in oligosaccharides is an important step in their detailed structural analysis. An approach is described that provides greater confidence in linkage determination for linear oligosaccharides based on multiple-stage tandem mass spectrometry (MSⁿ, n >2) and collision-induced dissociation (CID) of Z₁ ions in the negative ion mode. Under low energy CID conditions, disaccharides ¹⁸O-labeled on the reducing carbonyl group gave rise to Z₁ product ions (m/z 163) derived from the reducing sugar, which could be mass-discriminated from other possible structural isomers having m/z 161. MS³ CID of these m/z 163 ions showed distinct fragmentation fingerprints corresponding to the linkage types and largely unaffected by sugar unit identities or their anomeric configurations. This unique property allowed standard CID spectra of Z₁ ions to be generated from a small set of disaccharide samples that were representative of many other possible isomeric structures. With the use of MSⁿ CID (n = 3 – 5), model linear oligosaccharides were dissociated into overlapping disaccharide structures, which were subsequently fragmented to form their corresponding Z₁ ions. CID data of these Z₁ ions were collected and compared with the standard database of Z₁ ion CID using spectra similarity scores for linkage determination. As the proof-of-principle tests demonstrated, we achieved correct determination of individual linkage types along with their locations within two trisaccharides and a pentasaccharide.

A Practical and Enantiospecific Synthesis of (−)‐(R)‐ and (+)‐(S)‐Piperidin‐3‐ols

A highly enantiospecific, azide‐free synthesis of (?)‐(R)‐ and (+)‐(S)‐piperidin‐3‐ol in excellent yield was developed. The key step of the synthesis involves the enantiospecific ring openings of enantiomerically pure (R)‐ and (S)‐2‐(oxiran‐2‐ylmethyl)‐1H‐isoindole‐1,3(2H)‐diones with the diethyl malonate anion and subsequent decarboxylation.     

A phenolic glycoside from artemisia sacrorum

A phenolic glycoside has been isolated from Artemisia sacrorum grown in the Northeast of China. This compound is identified to be 4-O-β-D-glucopyranosyl-2-O-methylphloroacetophenone by means of nmr spectroscopy and synthesis.     

Synthesis of Quinoline Analogs: Search for Antimalarial Agents

Summary. Novel synthesis routes for the promising antimalarial agents 4(3-hydroxypyrrolidin-1-yl) and 4(3-hydroxypiperidine-1-yl)-2,8-bis(trifluoromethyl)quinoline have been developed.     

Effect of substitution of Ce on superconducting properties of Bi1.7Pb0.3Sr2Ca2−x Ce x Cu3O10+δ system

We have investigated the superconducting properties of the Bi_1.7 Pb_0.3Sr₂Ca_2−xCe _x Cu₃O_10+δ system with x=0.00, 0.02, 0.04, 0.08 and 0.1 by X-ray diffraction and magnetic susceptibility. The substitution of Ce for Ca has been found to drastically change the superconducting properties of the system. X-ray diffraction studies on these compounds indicate decrease in the c-parameter with increased substitution of Ce at Ca site and volume fraction of high T _c (2 : 2 : 2 : 3) phase decreases and low T _c phase increases. The magnetic susceptibility of this compound shows that the diamagnetic on set superconducting transition temperature (onset) varies from 109 K to 51 K for x=0.00, 0.02, 0.04, 0.08 and 0.1. These results suggest the possible existence of Ce in a tetravalent state rather than a trivalent state in this system; that is, Ca²⁺ → Ce⁴⁺ replacement changes the hole carrier concentration. Hole filling is the cause of lowering T _c of the system.     

Iodine-mediated facile dehydrogenation of dihydropyridazin-3(2H)one

A new protocol for the dehydrogenation of dihydropyridazin-3(2H)-one has been carried out by catalytic amount of iodine in dimethyl sulphoxide in good yield with easy workup.     

THE HADAMARD INEQUALITY FOR CONVEX FUNCTION VIA FRACTIONAL INTEGRALS

In this paper, we establish several inequalities for some differantiable mappings that are connected with the Riemann-Liouville fractional integrals. The analysis used in the proofs is fairly elementar...