Theoretical determination of the ionization potentials of the 1σ and 2σ electrons of CO(Σ)

Large-basis-set calculations of near Hartree-Fock accuracy were performed on CO⁺(1σ-hole ²Σ⁺) and CO⁺)2σ-hole, ²Σ⁺); correlation energies for these systems and for CO were calculated using an atoms-in-molecule approach, relativistic energies and vibrational structure corrections were also considered. The results are: IP(CO, 1σ) = 542.4 (542.57) eV, IP(CO,2σ) = 297.0 (296.24) cV, D_c(CO, ¹Σ⁺) = 10.8 (11.1) Ev, D₃(CO⁺, 1σ, ²Σ⁺) = 11.9 eV, D_e(CO⁺, 2σ, ²Σ⁺) = 9.1 eV, where IP and D_e stand respectively for ionization potential and dissociation energy, and where the numbers in parentheses refer to the most recent experimental values. The electron transfers resulting from the ionization of inner-shell electrons are discussed. Finally a quantitative correlation is developed correlating absolute chemical shifts to charge densities. Agreement between the calculated values and those derived from the correlation is quite satisfactory.     

The beryllium dimer potential

The convergence of ab initio calculations of the beryllium dimer potential is examined with several basis sets orders of perturbation theory. When the atomic pair natural orbital basis set calculations are extrapolated to the complete basis set and full CI limits, the calculated parameters: R_e=2.447 Å, D_e=827 cm⁻¹, ν₀₁=212.7 cm⁻¹, ν₁₂=167.2 cm⁻¹, ν₂₃=121.5 cm⁻¹ and ν₃₄=77.7 cm⁻¹ are in good agreement with the experimental parameters: R_e=2.45 Å, D_e=839±10 cm⁻¹, ν₀₁=223.2 cm⁻¹, ν₁₂=169.7 cm⁻¹, ν₂₃=122.5 cm⁻¹, and ν₃₄=79 cm⁻¹.     

The ν3 infrared spectrum of the He---NH4 complex

The mid-infrared spectrum of the ionic complex He---NH₄⁺ has been recorded in the vicinity of the triply degenerate ν₃ (t₂) vibration of the free ammonium ion. Apart from a small blue shift (≈ 0.7 cm⁻¹), the spectrum of the complex closely resembles that of the monomer. Ab initio calculations predict a vertex-bound minimum structure with an intermolecular well depth D_e ≈ 150 cm⁻¹, a center-of-mass separation of R_e ≈ 3.17 Å and barriers for internal rotation less than 30 cm⁻¹.     

All electron ab initio investigations of the electronic states of the MoN molecule

The low lying electronic states of the molecule MoN were investigated by performing all electron ab initio multi-configuration self-consistent-field (CASSCF) calculations. The relativistic corrections for the one electron Darwin contact term and the relativistic mass-velocity correction were determined in perturbation calculations. The electronic ground state is confirmed as being ⁴∑⁻. The chemical bond of MoN has a triple bond character because of the approximately fully occupied delocalized bonding π and σ orbitals. The spectroscopic constants for the ground state and ten excited states were derived. The excited doublet states ²∑⁻, ²Γ, ²Δ, and ²∑⁺ are found to be lower lying than the ⁴Π state that was investigated experimentally. Elaborate multi-configuration configuration-interaction (MRCI) calculations were carried out for the states ⁴∑⁻ and ⁴∏ using various basis sets. The spectroscopic constants for the ⁴∑⁻ ground state were determined as r_e=1.636 Å and ω_e=1109 cm⁻¹, and for the ⁴∏ state as r_e=1.662 Å and ω_e=941 cm⁻¹. The values for the ground state are in excellent agreement with available experimental data. The MoN molecule is polar with a charge transfer from Mo to N. The dipole moment was determined as 2.11 D in the ⁴∑⁻ state and as 4.60 D in the ⁴∏ state. These values agree well with the revised experimental values determined from molecular Stark spectroscopic measurements. The dissociation energy, D_e, is determined as 5.17 eV, and D₀ as 5.10 eV.     

Cationic and anionic states of CF, CCl, SiF and SiCl. Some new information derived using translational energy spectroscopy

Translational-energy spectroscopy was applied to collisional-excitation and charge-inversion reactions of CF⁺, CCl⁺, SiF⁺ and SiCl⁺ in order to gain energetic and bond-length information about the anionic and excited-cationic states of the title molecules. The excitation spectra revealed that the ã³Π state, known in CCl⁺ and SiCl⁺, has a term energy of 4.85 ± 0.15 eV in CF⁺ and 4.70 ± 0.20 eV in SiF⁺, while the 1¹Π state, known in CCl⁺, is not below the dissociation threshold in CF⁺, SiF⁺ and SiCl⁺. These data, and bond-length estimates for the ã³Π states, are consistent with documented ab initio predictions except for r_e of CF⁺(ã³Π) which seems to be larger than 1.21 Å. Charge-inversion spectra indicated that beams of monohalide cations formed from the tetrahalides, contained substantial proportions of ã³Π-state ions, and, in the case of CCl, SiF and SiCl, the broadness of spectral peaks was taken as evidence for the stability of the ã¹Δ-state anion. Adiabatic electron affinities were deduced to be 0.49 ± 0.15 eV, 0.89 ± 0.20 eV, 1.34 ± 0.30 eV and 1.40 ± 0.30 eV for the title molecules, respectively.     

Identification of a new progression of the Cl2 molecule with Σu symmetry

Synchrotron radiation is used to excite selectively the chlorine molecule in a Ne buffer gas. Due to the fast relaxation induced by the buffer gas, in the excitation spectrum of the D′→A′ emission at 258 nm, a new progression is observed. It is attributed to the 3 ¹Σ_u⁺ state which is the result of an avoided crossing between the Rydberg state π_g→5pπ and the valence state (1441) (σ_g→σ_u). It is characterized by T_e=83251 cm⁻¹, ω_e=783 cm⁻¹, ω_ex_e=29.6 cm⁻¹ and r_e=1.844 Å.     

Some further considerations on deriving matrix elements of non-periodic potentials in the basis of the non-degenerate harmonic oscillator wavefunctions

Using the properties of the generating function of the Hermite polynomials, we have calculated the matrix elements for the Gaussian-type potential V_G(x)=A exp{−B(x−C)²} and for the Morse-type potential V_M(x)=D_e[1−exp(−ax)]² in the basis of the non-degenerate harmonic oscillator wavefunctions. The final forms of these matrix elements are very simple to use and hence suitable for the numerical resolution of the Schrödinger equation for multiple-well potentials or anharmonic oscillators.     

An ab initio close-coupling calculation of the lower vibrational energies of the HCl dimer

We have previously determined an analytical ab initio six-dimensional potential energy surface for the HCl dimer, and in the present paper we use this potential, with the HCl bond lengths held fixed, in a full (four-dimensional) close-coupling calculation to determine the energies of the lowest 24 vibrational states. These vibrational states involve the intermolecular stretch ν₄, the trans-bend tunneling vibration ν₅, and the torsion ν₆. The highest of the 24 levels is the (ν₄ν₅ν₆)=(111) state, for which we calculate an energy of 200 cm⁻¹ above the (000) state. As well as determining tunneling energies up to 5ν₅=183 cm⁻¹, we determine ν₄=49 cm⁻¹, 2ν₄=93 cm⁻¹, 3ν₄=134 cm⁻¹, 4ν₄=172 cm⁻¹, ν₆=137 cm⁻¹ and ν₄+ν₆=178 cm⁻¹, together with tunneling energies in all these states. Making allowance for the HCl stretching zero-point energy we determine the dissociation energy D₀ as 390 cm⁻¹ on this analytical surface. We determine that below 300 cm⁻¹ there are 72 vibrational (J=K=0) states, and below dissociation there are 162 vibrational (J=K=0) states, for this potential surface.     

Density functional theory analysis of CaRgn complexes: (Rg=He, Ne, Ar; n=1–4)

CaRg_n⁺ (Rg=He, Ne, Ar) complexes with n=1–4, are investigated by performing using the B3LYP/6-311+G (3df) density functional theory calculations. The CaHe_n⁺ (n=1–4) complexes are found to be stable. In the case of CaNe_n⁺ and CaAr_n⁺, stable structures and stationary point were found only for n=1 and 2. For n=3 in the C_3V and the D_3h point group as well as for n=4 in the T_d (tetrahedral) point group a saddle point (imaginary frequency) is observed and global minimum could be obtained along the potential energy surface.     

聚乙烯醇二维光子晶体水凝胶的制备及乙醇响应行为

以单分散的聚苯乙烯微球乳液为原料, 采用针尖注射法制备了聚苯乙烯二维光子晶体阵列, 采用聚乙烯醇填充二维光子晶体阵列, 以戊二醛为交联剂, 得到聚乙烯醇二维光子晶体水凝胶(PVA·2DPCH). 通过测定PVA·2DPCH在不同浓度的乙醇/水溶液中的德拜环直径(D)变化, 研究了PVA·2DPCH对乙醇的响应行为. 结果表明, 在乙醇体积分数为0~60%范围内, PVA·2DPCH对乙醇没有明显响应, 德拜环直径基本保持不变; 当乙醇体积分数超过60%时, PVA·2DPCH对乙醇表现出敏感响应, 其德拜环直径随乙醇体积分数的增大而增大, 响应时间仅需30 s; 在乙醇体积分数为60%~100%范围内, PVA·2DPCH的德拜环直径变化(ΔD)与乙醇体积分数(V_e)呈线性相关: 当60%≤V_e≤75%时, 其线性回归方程为ΔD=50.30V_e-31.74, r²=0.9734; 当75%<V_e≤100%时, 其线性回归方程为ΔD=111.14 V_e-74.03, r²=0.9902. 以制备的PVA·2DPCH为乙醇传感器, 利用德拜环法测定市售酒精消毒液中乙醇含量, 方法简单快速, 兼具无标记、 可视化检测的特点.     

Photodissociation spectroscopy of Mg—Ar

Mg⁺—Ar ion—molecule complexes are produced in a pulsed supersonic nozzle cluster source. The complexes are mass selected and studied with laser photodissociation spectroscopy in a reflectron time-of-flight mass spectrometer system. An electronic transition assigned as X ²Σ⁺ → ²Π is observed with an origin at 31387 cm⁻¹ (vac) for ²⁴Mg⁺—Ar. The ²⁴Mg⁺—Ar spectrum is characterized by a 15 member progression with a frequency (ω′_e) of 272 cm⁻¹. An extrapolation of this progression fixes the excited state dissociation energy (D′_o) at 5552 cm⁻¹. The corresponding ground-state value (D″_o) is 1270 cm⁻¹ (3.6 kcal/mol). The ²Π _, spin—orbit splitting is 76 cm⁻.     

A new singlet state of Te2

The 4067 Å line of the krypton-ion laser covers two transitions in the BO⁺_u-X O⁺_g system of ¹³⁰Te₂, R(36) in the 16-0 band and R(172) in the 18-0 band. Subsequent fluorescence has been recorded by Fourier transform spectrometry in the range 5900 to 15000 cm⁻¹. Many transitions, with v' in the range 0 to 47, have been assigned to a new system, B O⁺_u-b¹ ∑⁺_g, and vibrational and rotational constants for the new state have been derived. The value of T_e for b ^I∑_g⁺ is about 9600.2 cm⁻¹.     

Conformational and structural analysis of N-N′-bis(4-methoxybenzylidene)ethylenediamine

The Schiff base compound, N-N′-bis(4-methoxybenzylidene)ethylenediamine (C₁₈H₂₀N₂O₂) has been synthesized and its crystal structure has been investigated by X-ray analysis and PM3 method. The compound crystallizes in monoclinic space group P2₁/n with a=10.190(1), b=7.954(1), c=10.636(1) Å, β=111.68(1)°, V=801.1(1) ų, Z=2 and D_cal=1.229 Mgm⁻³. The title structure was solved by direct methods and refined to R=0.056 for 2414 reflections [I>3.0σ(I)] by full-matrix anisotropic least-squares methods. The energy profile of the compound was calculated by PM3 method as a function of θ[N1′–C9′–C9–N1]. The most stable molecular structure of the title compound is the anti conformation, which is different in energy by 5.0 and 1.0 kcal mol⁻¹ from the eclipsed conformation I and gauche conformations, (III and V), respectively.     

Prediction of the concentration polarization in the nanofiltration/reverse osmosis of dilute multi-ionic solutions

The aim of this work was to develop a simple and accurate model for predicting the concentration polarization index in the nanofiltration (NF)/reverse osmosis (RO) of dilute multi-ionic solutions. On the grounds of this model, the total flux of the ion i at the feed-solution/membrane interface consists of the sum of the diffusion, convection and migration fluxes, the former of which is determined by conventional mass-transfer correlations duly corrected to take into account the permeation through the membrane (suction effect). The coupling of the ionic fluxes is enforced by the electroneutrality requirement at the feed-solution/membrane interface. The model developed dispenses with the arbitrary assumption of the thickness of a film layer in the vicinity of the membrane surface.

Assessing the accuracy/validity of this model with multi-ionic solutions would be rather harsh, thus the model accuracy and ranges of validity were ascertained for a benchmark case: NF/RO of single salt solutions. The model predicts approximate concentration polarization indexes of the salts A⁺B⁻, A⁺₂B²⁻ and A⁺₃B³⁻ (or A²B⁻₂ and A³⁺B⁻₃) with positive deviations lower than 10% with respect to the benchmark concentration polarization index, for ions diffusivities ratios, D₁/D₂ (or D₂/D₁), in the range 0.16–5.5 and ≡J_v/k_c<3, where J_v is the permeation flux and k_c is the mass-transfer coefficient of the salt for vanishing mass-transfer rates at impermeable walls. The main assumption of the model – the individual mass-transfer coefficients of the ions are independent of each other – appears to hold in a broad range of conditions, for single salt solutions.

The model developed was expeditely applied to predict the concentration polarization in the nanofiltration of solutions containing Na⁺, Cl⁻ and a dye³⁻ (experimental data of Bowen and Mohammad [AIChE J. 44 (8) (1998) 1799–1812]), and its predictions are in fair agreement with the predictions of the extended Nernst–Planck equations in the film layer of the “slowest” ion.     

MRD CI study on the low-lying states of AlP

Large-scale MRD CI calculations assign to AlP the ground state X ³Σ⁻ (9σ²3π²) and a close-lying state 1 ³Π (9σ3π³) (T_e = 0.08 eV). Up to transition energies of 2.0 eV, other states are described by the configurations 9σ3π³ (1¹Π), 8σ²3π⁴ (1 ¹Σ⁺), 9σ²3π² (1 ¹Δ and 2 ¹Σ⁺) and 9σ3π²4π (1 ⁵Π). The 2 ³Π state, located at ≈ 2.30 eV, shows a shallow double minimum. Numerous perturbations are expected to induce predissociation upon 2 ³Π. Multiplets arising from the occupation 8σ²3π³4π are clustered in the 3.25–3.50 eV region. Quintet states with the configuration 8σ9σ3π³4π are bound, with T_e values (in eV) of 3.80 (1 ⁵Σ⁺), 4.44 (1 ⁵Δ) and 4.88 (3 ⁵Σ⁻), respectively. The 9σ → 4s Rydberg members ⁵Σ⁻ and ³Σ⁻ lie in the 4.58–4.72 eV energy region. The first ionization potential (ionization to X⁴Σ⁻ of AlP⁺, 9σ → ∞) is estimated to be 7.65 eV. Ionization to the 1 ²Σ⁻ and 1 ²Π states of AlP⁺ is suggested to occur between 8.0 and 8.8 eV. The dipole moments of X ³Σ⁻, 1 ¹Δ and 2 ¹Σ⁺ are close to 1.0 D, whereas the 1 ¹Σ⁺ state has μ = 3.49 D; 1 ³Π and 1 ¹Π have dipole moments from 2.45 to 2.91 D. All low-lying states show a polarity Al⁺P⁻. Finally, the electronic structure and transition energies of AlP are compared with those of the isoelectronic species BN, AIN, and SiP⁺.     

Millimeter-wave rotational spectrum and molecular constants of diatomic gallium iodide

The gas-phase molecular spectrum of Gal has been detected in the millimeter wavelength region. The molecules are produced by vapourising a mixture of gallium and lead iodide into an evaculated cell. Analysis of the observed rotational transitions yields the following molecular parameters for ⁶⁹Ga¹²⁷I: Y₀₁ = 1706.89645(83) MHz, Y₁₁ = −5.68714(53) MHz, Y₂₁ = 6.329(43) kHz, Y₀₂ = −0.472713(60) kHz, Y₁₂ = 0.472(38) Hz, ω_e = 216.38 cm⁻¹, ω_e^x_e= 0.471 cm⁻¹, and for ⁷¹Ga¹²⁷I: y₀₁ = 1675.72004(71) MHz, Y₁₁ = −5.53277(57) MHz, Y₂₁ = 5.995(34) kHz, Y₀₂ = −0.455700(51) kHz, y₁₂ = 0.522(40) Hz, ω_e = 214.37 cm⁻¹, and ω_e^x_e = 0.458 cm⁻¹. The equilibrium internuclear distance obtained for Gal is r_e = 2.574667(12) Å.     

All electron fully relativistic Dirac–Fock calculation for darmstadtium carbide using prolapse free basis set

For the first time, ab inito all electron fully relativistic and correlated Dirac–Fock calculations with prolapse free basis set are reported for a Super Heavy Element. We investigated the relativistic effects on bonding and on some spectroscopic constants for the darmstadtium carbide and our results at DF/CCSD(T) with a prolapse free basis set suggest for R_e, ω_e and D_e the values of 174 pm, 1114 cm⁻¹ and 7.29 eV, respectively. These values are very similar to the values for PtC found on literature. It was also found that prolapse free basis set may be important to estimate the dissociation energy using Relativistic 4-components correlated methods.     

Structures and energetics of C3H6S isomers: a Gaussian-3 ab initio study

Twenty-two isomers/conformers of C₃H₆S^+√ radical cations have been identified and their heats of formation (ΔH_f) at 0 and 298 K have been calculated using the Gaussian-3 (G3) method. Seven of these isomers are known and their ΔH_f data are available in the literature for comparison. The least energy isomer is found to be the thioacetone radical cation (4⁺) with C_2v symmetry. In contrast, the least energy C₃H₆O^+√ isomer is the 1-propen-2-ol radical cation. The G3 ΔH_f298 of 4⁺ is calculated to be 859.4 kJ mol⁻¹, ca. 38 kJ mol⁻¹ higher than the literature value, ≤821 kJ mol⁻¹. For allyl mercaptan radical cation (7⁺), the G3 ΔH_f298 is calculated to be 927.8 kJ mol⁻¹, also not in good agreement with the experimental estimate, 956 kJ mol⁻¹. Upon examining the experimental data and carrying out further calculations, it is shown that the G3 ΔH_f298 values for 4⁺ and 7⁺ should be more reliable than the compiled values. For the five remaining cations with available experimental thermal data, the agreement between the experimental and G3 results ranges from fair to excellent.

Cation CH₃CHSCH₂^+√ (10⁺) has the least energy among the eleven distonic radical cations identified. Their ΔH_f298 values range from 918 to 1151 kJ mol⁻¹. Nevertheless, only one of them, CH₂=SCH₂CH₂^+√ (12⁺), has been observed. Its G3 ΔH_f298 value is 980.9 kJ mol⁻¹, in fair agreement with the experimental result, 990 kJ mol⁻¹.

A couple of reactions involving C₃H₆S^+√ isomers CH₂=SCH₂CH₂^+√ (12⁺) and trimethylene sulfide radical cation (13⁺) have also been studied with the G3 method and the results are consistent with experimental findings.     

Structural characterisation of [Pt(NH3)4]2[W(CN)8][NO3]·2H2O donor–acceptor complex

The bimetallic [Pt(NH₃)₄]₂[W(CN)₈][NO₃]·2H₂O is characterised by single-crystal X-ray diffraction [S.G.P2₁/m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D_4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D_4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1)^* separations of 4.77(2), 4.55(2)^* and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO₃⁻ between parallel [Pt(1)(NH₃)₄]²⁺ planes and the second consists of [W(CN)₈]³⁻ interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH₃)₄]²⁺. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH₃ ligands, water molecules and oxygen atoms of NO₃⁻ counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer.     

Analysis of the diffuse bands near 6100 Å in the fluorescence spectrum of Cs2

The diffuse bands near 6100 Å in the laser-induced fluorescence spectrum of Cs₂ are analyzed through quantum-mechanical spectral simulations. These bands are interpreted as bound-free emission to the vibrational continuum of the ground state from an excited state of ion-pair character. The lower region of this state, which we have labeled E′, is described approximately by the spectroscopic constants, T_e = 19400 cm⁻¹, R_e = 9 Å, and ω_e = 13 cm⁻¹. Experiments with a single-mode Ar⁺ laser as excitation source clearly reveal fine structure in the E′ → X spectrum, which was not evident for multimode laser excitation. This fine structure confirms our analysis and supports our suggestion that extensive averaging over initial (υ′, J′) levels is responsible for the absence of fine structure in the spectra excited by a multimode laser. Various averaging mechanisms are investigated in the spectral calculations. The paper includes a brief review of other work on “structured continua” in diatomic spectra, and a semiclassical treatment of such structure, with emphasis on the distinction between “reflection” structure and “interference” structure.