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1.
Debates continue on the applicability of the Young–Laplace equation for droplets, vapor bubbles and gas bubbles in nanoscale. It is more meaningful to find the error range of the Young–Laplace equation in nanoscale instead of making the judgement of its applicability. To do this, for seven liquid argon drops (containing 800, 1000, 1200, 1400, 1600, 1800, or 2000 particles, respectively) at T = 78 K we determined the radius of surface of tension Rs and the corresponding surface tension γs by molecular dynamics simulation based on the expressions of Rs and γs in terms of the pressure distribution for droplets. Compared with the two-phase pressure difference directly obtained by MD simulation, the results show that the absolute values of relative error of two-phase pressure difference given by the Young–Laplace equation are between 0.0008 and 0.027, and the surface tension of the argon droplet increases with increasing radius of surface of tension, which supports that the Tolman length of Lennard-Jones droplets is positive and that Lennard-Jones vapor bubbles is negative. Besides, the logic error in the deduction of the expressions of the radius and the surface tension of surface of tension, and in terms of the pressure distribution for liquid drops in a certain literature is corrected.  相似文献   

2.
Previously published values of state-to-state integral inelastic cross sections for the H2(Ji)—M (M  H, He, Li, Li+, H2, CO2) systems are fitted to the exponential gap relation for the rotational inelastic process to obtain the C value that reflects the magnitudes of relative cross sections. While the vibration of the rotor seems to have little influence, the C value is shown to decrease dramatically with increase in initial collision energy Ti, ΔCTi being larger at lower Ti for all systems analysed, in accord with the prediction of the surprisal synthesis of Procaccia and Levine. For the only case of H2(Ji)-Li+ for which results are available for several Ji, C decreases with increase in Ji or Ji(Ji + 1)). The C value predicted by Procaccia and Levine for H2M systems falls within the range of C values calculated for the various collision partners. However, there is a noticeable change in C (albeit within a factor of two) with change in M, indicating that dynamical factors do play an important role in rotational inelastic processes.  相似文献   

3.
The linear equation connecting the one-bond spin–spin coupling constants between carbon nuclei, JCC, and the product of the electronegativities of substituents at the CC triple bond is derived using a large number of data for variously substituted acetylenes. The equation 1JCC = 23.23 Ex·Ey + 15.45 provides a means for estimation of unknown 1JCCs and for calculation (and/or verification) of electronegativities of substituents. The equation allows one to estimate a total range of about 350 Hz for 1JCCs. The smallest value (30 Hz) is predicted for dicaesium acetylide, Cs2C2, and the largest one for difluoroacetylene, F2C2 (383 Hz). The electronegativities of tin and lead, which constituted a subject of long-lasting controversy in the literature, calculated using the equation are equal to 1.74 and 1.64, respectively.  相似文献   

4.
《Chemical physics letters》1986,124(2):105-109
Fluorescence excited in the A1Σ+ -X1Σ+ system of 39KH by the 4880 Å argon-ion laser line gives information about the ground state as far as the last bound rovibrational level. This is identified as J = 6 in v = 23, and, assuming a limit midway between J = 6 and J = 7, De(KH) = 14776 ± 4 cm−1.  相似文献   

5.
Detailed studies of the Raman and infrared line parameters of AgNO3?CH3CN systems ranging from dilute solutions to 9M are reported. A concentration quotient of 1.1M ?1 was obtained for the formation of the Ag+NO 3 ? ion pair when C<4M. The complex appears to have point group CsV) with Ag+ in a “roll-on” position. The Ag+ ion is solvated by four molecules of CH3CN; nitrate ion replaces three of these when bound to Ag+. When C>4M, multiple ion aggregates form in the solution. A low-frequency 110 cm?1 line is ascribed to librational motions of NO 3 ? , probably bound to Ag+.  相似文献   

6.
《Chemical physics》1987,118(3):437-444
Fluorescence decay profiles of NO excited levels slightly above the dissociation limit have been measured by a single-photon counting technique with nanosecond pulse excitation using an iodine flash lamp. Three iodine atomic lines in the vicinity of 180 nm are found to bring NO molecules into the levels A2Σ+(ν = 5, N = 9), B22Π32(ν = 8, J = 8.5), C2Π32(ν = 1, J = 8.5), D2Σ+(ν = 0, N = 5) and D2Σ+(ν = 1, N = 9). Extrapolated zero-pressure lifetimes for single rotational levels are obtained, except for the C state where only a lifetime of ⩽0.4 ns was obtained. Self-quenching rate constants are also determined under higher-pressure conditions. Helium was found to quench the NO A2Σ+(ν′ = 5) fluorescence very efficiently.  相似文献   

7.
《Polyhedron》2007,26(9-11):2135-2141
By using broken-symmetry hybrid-DFT (UB3LYP and UB2LYP) calculation, the effective exchange integrals (J values) of [Cr(C5(CH3)5)2]+[TCNE][Cr(C5(CH3)5)2]+ and [Mn(C5(CH3)5)2]+[TCNQ][Mn(C5(CH3)5)2]+ were determined theoretically. Those calculated models were reduced to 3-spin-sites models from X-ray crystallographic data of charge transfer 3D crystal. The calculated results showed that effective exchange integrals were positive and the signs of spin densities on the cyclopentadienyl rings were negative. These results supported the so-called McConnell I mechanism for ferromagnetism proposed by Kollmar et al. and our previous calculations. Natural orbital analysis made it clear that the orbital overlap between SOMO on metals and SOMO on TCNE or TCNQ cations was nearly zero. These results indicated that orbital orthogonality was an important key factor for explaining the ferromagnetism of those systems.  相似文献   

8.
Photoelectron energy and angular distributions are measured for the 2+1 multiphoton ionization process H2 X1Σg+ (ν = 0,J) + 2hv → E,F1Σg+E,JE = J) + hν → H2+X2Σg++) + e?, for νE = 0, 1, or 2 and for JE = 0 or 1 of the inner well of the double-minimum E,F state. Although a strong preference is found for ν+ = νE, the detailed H2+ vibrational distribution does not exhibit Franck-Condon behavior, and the photoelectron angular distributions vary markedly with both the JE value of the intermediate state and the ν+ value of the ion.  相似文献   

9.
The i.r. and Raman spectra of (CH3)3NCH2Cl+Cl(I), (CH3)3NCH2Br+Br(II) and (CH3)3NCH2J+J(III) are measured and particularly discussed in relation to the skeletal vibrations.  相似文献   

10.
Young equation is the fundamental equation of wetting theory in which the connection among the surface tensions, \(\gamma _{{\varphi \psi }} \) and the contact angle, θ L, are given. The surface tension of solid surfaces, however, cannot be obtained directly from the Young equation. In this paper, the application of the individual representation theory is demonstrated for the determination of surface tensions of solids (or any phase pair) using experimentally obtained contact angle data. According to this approach, the state of the interfacial layers depends upon, by definition, the properties of the bulk phases in every heterogeneous system, and thus, it complements the traditional capillary theory.  相似文献   

11.
All J(P? H) and J(P? C) values, including signs, have been obtained in acetylenic and propynylic phosphorus derivatives, R2P(X)? C?C? H and R2P(X)? C?C? CH3 (X ? oxygen, lone pair and R ? C6H5, N(CH3)2, OC2H5, N(C6H5)2, Cl) from 1H and 13C NMR spectra. In PIV derivatives the following signs are obtained: 1J(P? C)+, 2J(P? C)+, 3J(P? C)+, 3J(P? H)+, 4J(P? H)? . Linear relations are observed between 1J(P? C), 2J(P? C) and 3J(P? C) versus 3J(P? H), indicating that these coupling constants are mainly dependent on the Fermi contact term, though the other terms of the Ramsey theory do not seem to be negligible for 1J(P? C) and 2J(P? C). In PIII derivatives these signs are: 1J(P? C)- and +, 2J(P? C)+, 3J(P? C)-, 3J(P? H)-, 4J(P? H)+. Only 3J(P? C) and 3J(P? H) reflect a small contribution of the Fermi contact term while in 1J(P? C) and 2J(P? C) this contribution seems to be negligible relative to the orbital and/or spin dipolar coupling mechanisms.  相似文献   

12.
Isopropanol displacement under nitrogen pressure was used for the determination of pore size distribution in microfiltration polypropylene hollow fibres. Applying various assumptions about gas transport process two completely different characteristics of pore sizes were obtained. To verify these results an analysis of SEM images of the investigated membrane was conducted concerning its porous structure (pore diameters, surface occupied by pores). According to the SEM analysis the mean coverage of membrane surface by pore entrances should be about 20% of total area. For the distribution which accounted for pore evacuation according to Young–Laplace equation with contact angle θ=67° surprisingly dense coverage amounting to over 70% of total surface (by calculated total pore number over 1013 per m2) was predicted. Results for the distribution which accounted for gas bubble formation at the membrane surface (equivalent to θ=0°) fit into the expected range of pore numbers and membrane coverages (about 1011 per m2 and about 10%, respectively). It is concluded that the mechanism of bubble formation, determined by an actual pressure, liquid surface tension and pore size, is the crucial process while the value of contact angle θ does not play any role in the determination of pore size distribution.  相似文献   

13.
With the aim of improving flux pinning and in-field critical current density [JC(H)], two physically and chemically different additives – burned rice husk (BRH) and nano Ho2O3 were introduced into in situ MgB2 superconductor. The effects of the above two additives were studied individually and combinedly. Ho2O3 decomposed and reacted with B to form HoB4, without any substitution. BRH caused considerable amount of C substitution at B site and formed Mg2Si and Mg2C3 secondary phases. Addition of Ho2O3 improved the JC(H) only marginally, but BRH improved the JC(H) strongly. Combined addition of Ho2O3 with BRH was found to be much more effective than their solo addition for the enhancement of JC(H) of MgB2.  相似文献   

14.
This paper presents the contemporary state-of-art of the phenomenological thermodynamic theory of the thin foam and emulsion films, both symmetrical and asymmetrical ones. The roots of this theory are in the Gibbs' theory of capillarity. Two basic approaches — with two Gibbs dividing surfaces and with three surfaces of tension, are described. The generalization of the theory for systems with more complex geometry is commented. The ways of determining of the thermodynamic thickness of the film are described. The basic thermodynamic quantities of the thin film: disjoining pressure, tension of the film and surface tension of the film, are defined. The tangential mechanical equilibrium conditions with two types of contact angles, θh, and θ0, are discussed. The effect of line tension of the three-phase contact-line perimeter on the film contact angles is elucidated.  相似文献   

15.
《Chemical physics letters》1987,138(6):575-578
The angular dependence of the Doppler profile of the Balmer-β line indicates that the asymmetry parameter, b, is positive and the polarization of the electric vector, Jp, is 0.7 ± 0.1 for the formation of H1(n=4) from H2. Thus, H1(n=4) is produced in a parallel transition, and the transition moment of H1 lies along the dissociation axis. This result suggests that the intermediate states for the fast and anisotropic H1(n=4) atoms should be of the type 1Σ+u(2pσu)(ng).  相似文献   

16.
A. Poniewierski 《Liquid crystals》2013,40(10):1369-1380
A nematic liquid crystal in contact with a solid substrate is studied in the partial wetting regime. Both a mesoscopic Landau-de Gennes theory and a macroscopic effective interface Hamiltonian approach are considered. A generalized Young equation for the balance of forces at the three-phase contact line is derived, which takes into account corrections due to distortions of the nematic director field. It is also shown that the asymptotic form of the separation of the nematic-isotropic interface from the substrate has a logarithmic correction to the usual linear behaviour. The characteristic length scale of this correction is given by the ratio K/(2σNI), where K and σNI are the average elastic constant and the nematic-isotropic surface tension, respectively, and is of the order of a few hundred angstroms. Then, a simple form of an effective interface Hamiltonian is proposed, and results consistent with the predictions of the Landau-de Gennes theory are obtained. It is shown, in the framework of this macroscopic approach, that the line tension associated with the contact line remains finite, when the thermodynamic limit is taken, if the anchoring at both the nematic-substrate and the nematic-isotropic interfaces is homeotropic. However, in the case of different anchoring directions, the line tension diverges logarithmically with the system size.  相似文献   

17.
Sum-over-states perturbation calculations within the INDO framework are reported for 24 1J(FC) and 34 3J(FC) couplings. In general, satisfactory agreement with the experimental data is obtained when the integral products SF2(O) SC2(O) and 〈r?3Fr?3C take the values of 136.543 au?6 and 58.352 au?6, respectively, for the 1J(FC) couplings. The corresponding values for the 3J(FC) couplings are 29.520 au?6 and 44.340 au?6, respectively. All of the 1J(FC) values are predicted to be negative, whereas all of the 3J(FC) values are calculated with positive signs. The results indicate the importance of including the contact, orbital and dipolar contributions in the calculations.  相似文献   

18.
A series of novel cationic gemini surfactants, p-[C n H2n+1N+(CH3)2CH2CH(OH)CH2O]2C6H4·2Cl? [A(n = 12), B(n = 14) and C(n = 16)], containing a spacer group with two flexible and hydrophilic groups (2-hydroxy-1,3-propylene) on both sides of a rigid and hydrophobic group (1,4-dioxyphenylene) has been synthesized by the reaction of hydroquinone diglycidyl ether with N,N-dimethylalkylamine and N,N-dimethylalkylamine hydrochloride. Their surface-active properties have been investigated by surface tension measurement. The critical micelle concentration (cmc) values of the synthesized cationic gemini surfactants are one order of magnitude lower than those of their corresponding monomeric surfactants (C n H2n + 1N+(CH3)3·Cl?). Both the cmc and surface tension at the cmc (γcmc) of A are lower than those of p-[C12H25N+(CH3)2CH2]2C6H4·2Cl? (D). The novel cationic gemini surfactants A and B also show good foaming properties.  相似文献   

19.
Mn(TCNE)[C4(CN)8]1/2 (TCNE=tetracyanoethylene) and [NEt4]MnII3(CN)7 have extended layers with nearest neighbor intralayer S=5/2 and S=1/2 spin sites that couple antiferromagnetically forming ferrimagnetic layers. These layers are uniformly connected via diamagnetic (nonmagnetic) bridging μ4‐[(C4(CN)8]2? (8.77 Å) or μ‐CN (5.48 Å) ligands, respectively, that antiferromagnetic couple the ferrimagnetic layers resulting in an antiferromagnet. The Jinter/kB is ?1.0 and ?1.8 K (H=?JSi?Sj) for Mn(TCNE)[C4(CN)8]1/2 and [NEt4]MnII3(CN)7, respectively. Albeit intrinsically multilayered, these antiferromagnets have the same motif as that for artificial/synthetic antiferromagnets that exhibit giant magnetoresistance (GMR) and are commercially used in many magnetic memory applications.  相似文献   

20.
Salt effects on the aggregation behavior of tripolar zwitterionic surfactants in aqueous solutions have been investigated using surface tension, dynamic light scattering (DLS), freeze-fracture transmission electron microscopy (FF-TEM), and 1H NMR. The tripolar zwitterionic surfactants with different inter-charge spacers are [C14H29(CH3)2N+CsN+(CH3)2CH2CH2CH2SO3 ?]Br? (C14CsTri, Cs?=?–(CH2)2–, –(CH2)6–, –(CH2)10–, and p-xylyl). It is found that the critical micelle concentration (CMC) values of the corresponding traditional zwitterionic surfactant C14H29(CH3)2N+CH2CH2CH2SO3 ? (TPS) are almost constant with the increase of the NaBr concentration. However, the CMC values of C14CsTri decrease sharply at a lower NaBr concentration and then level off at a higher NaBr concentration. Moreover, the decreasing extents of the CMC values for C14C2Tri, C14C6Tri, and C14CpxTri are very close, but more significant than that for C14C10Tri, suggesting that the self-assembly ability of the tripolar zwitterionic surfactants with a longer inter-charge spacer is less sensitive to NaBr. The DLS and FF-TEM results reveal that C14C2Tri, C14C6Tri, and C14CpxTri form micelles without NaBr and that the size slightly increases with the increase of NaBr concentration, whereas micelles and vesicles coexist for C14C10Tri and TPS without NaBr and then transfer to micelles upon the addition of NaBr. The salt-induced morphological transition for C14C10Tri is further studied using 1H NMR. The addition of NaBr reduces both the electrostatic repulsion between the same charged ammoniums and the electrostatic attraction between the oppositely charged ammonium and sulfonate. Thus, the longer inter-charge spacer of C14C10Tri tends to be more bended and the sulfonate group becomes available to contact the ammonium, which promotes micellization.  相似文献   

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