Inertia-corrected budó treatment of dielectric relaxation in polar molecules: Application to the fir spectrum of acetonttrile and hexanone-2

The theory of dielectric relaxation of an assembly of molecules with neareit-neighbour dipole-dipole coupling, originally developed by Budó, is extended to include inertial effects. This yields an orientational correlation function that gives rise to Debye-type absorption in the microwave region and resonance absorption in the FIR region. The results are formally similar to the itinerant-oscillator model when the outer cage in that model carries a dipole moment. The results compare favourably with experimental observations on acetonitrile and hexanone-2.     

Models for intramolecular triplet exciton migration applied to vinyl aromatic polymers

Models for intramolecular triplet exciton migration have been developed for vinyl aromatic polymers. A one-dimensional model which allows only neighbor-to-neighbor migrations yields frequencies which are several orders of magnitude smaller than those predicted either by exchange or dipole-dipole mechanisms. An intramolecular model permitting three translational degrees of freedom predicts triplet exciton hop frequencies on the order of 10⁴ s⁻ in reasonable agreement with either exchange or dipole-dipole mechanisms.     

Far infrared spectra of mono- and bisphthalocyanine derivatives

The far infrared spectra of a series of unsubstituted monophthalocyanine (Pc) and di-Pc derivatives and some of the corresponding tetra-tert-butyl substituted Pc molecules are reported. The infrared data were recorded between 100 and 4.50 cm⁻¹. The vibrational assignment of metal-nitrogen stretching frequencies is discussed. The far infrared data for tert-butyl Pc derivatives and a group of C_4ν Pc complexes are presented here for the first time.     

Far infrared and millimetre-wave absorption spectra of some low-loss polymers

Absorption spectra in the range 2–50 cm⁻¹ are reported for polyethylene, polypropylene and 'TPX' (basically poly 4-methyl pentene-1). The former has no resonances in this region and the continuum absorption can be represented by a simple quadratic function of wavenumber which, when extrapolated to radio frequencies, gives a good account of the observed losses. Polypropylene and 'TPX' show discrete absorption bands, but for these too there appears to be an underlying continuum. The millimetre-wave absorption possibly arises from a summation of the high frequency wings of the radio region relaxations and the low frequency wings of the far infrared resonances plus an inherent continuum which may be analogous to the broad absorption shown by non-polar liquids in the far infrared.     

BaLaB9O16中Ce3+敏化Dy3+发光的机理

在紫外光激发下,研究了BaLaB₉O₁₆中Dy³⁺、Ce³⁺的发光光谱、激发光谱、发光强度及荧光寿命随着组成变化的规律性.结果表明;De³⁺对Dy³⁺的发光有相当强的敏化作用,Ce³⁺→Dy³⁺的能量传递效率可高达93%,能量传递的机理为电偶极-偶极相互作用的共振传递.根据349nm激发下Dy³⁺发光强度与浓度的关系,证明了Dy³⁺发光的自身浓度猝灭机理也为电偶极-偶极相互作用.     

Variational calculation of dynamic polarizabilities

The finite field method of obtaining static multipole polarizabilities is extended to the calculation of dynamic polarizabilities. The first-order frequency dependent wavefunction is obtained variationally using a trial function, λ(ω)ψ₁(0). ψ₁(0) is the first-order wavefunction obtained in the static calculation. The results are applied to the approximation of the dynamic polarizability at imaginary frequencies. These are then used to calculate the coefficients for the inverse power series representation of the interatomic potential energy. The method has been applied to two simple cases, hydrogen and helium. For hydrogen the present method yields results close to the exact values for the static dipole polarizability and the dipole-dipole van der Waals coefficient; C₆. In the case of helium a simple Hartree-Fock function was perturbed but the results are still encouraging with the dipole-dipole van der Waals coefficient, C₆, calculated to within 7% of the accurate value.     

Miscibility of polyester/nitrocellulose blends: A DSC and FTIR study

The miscibility of polyester/nitrocellulose blends was investigated by differential scanning calorimetry and Fourier-transform infrared (FTIR) spectroscopy. Two nitrocelluloses (NC) derived from wood and having different nitrogen contents (12.62 and 13.42%) were used. On the basis of the glass transition temperature criterion, poly(?-caprolactone) (PCL), poly(valerolactone), poly(ethylene adipate), and poly(butylene adipate) are miscible with nitrocellulose, whereas poly(α-methyl α-propyl β-propiolactone) and poly(α-methyl β-proiolactone) are immiscible. The T_g versus composition curves of PCL/NC blends do not follow a monotone function but exhibit a singular point at a critical PCL volume fraction of 0.51 for NC-1342 and 0.45 for NC-1262 in agreement with Kovacs' theory. A shift of 17 cm^-1 of the carbonyl stretching band was observed with PCL/NC blends and is taken as evidence for hydrogen bonding interaction between the PCL carbonyl group and NC hydroxyl group. The frequency difference between the free hydroxyl absorbance and the absorbances of the hydrogen-bonded species was found to be 85 cm^-1 in pure NC and 125 cm^-1 in PCL/NC blends; it indicates that the average strength of this interaction is stronger than the corresponding self-associated hydrogen bonding in pure NC. The presence of a dipole-dipole interaction between the nitrate-ester groups of NC and the carbonyl groups of the polyesters is reported. The relative strength of the hydrogen bonding and dipole-dipole interactions is discussed and correlated with polymer miscibility.     

The Temperature‐Dependent Hydrogen‐Bonding Signature of Lipids Monitored in the Far‐Infrared Domain

Phospholipids are studied by means of Fourier transform infrared (FTIR) spectroscopy in the mid‐ and far‐infrared spectral ranges, thereby establishing the hydrogen‐bonding continuum as a function of the temperature. The well‐known mid‐infrared spectrum of the phospholipid layer clearly shows a temperature‐dependent phase transition. In the far‐infrared region (from 300 to 50 cm^?1), an alternation of the interaction between the phospholipids and water molecules is found. The hydrogen‐bonding network ensemble and bound water molecules can be monitored in this spectral region. The lipid structure is found to strongly influence the intermolecular hydrogen‐bonding interplay. Thus, studies in the far‐infrared region provide significant information—at the molecular level—about the intermolecular hydrogen‐bonding signature of self‐assembled phospholipids.     

The laser Raman and infrared spectra of crystalline dibenzyl

The Raman spectrum of crystalline dibenzyl has been excited with a 50-mw He-Ne laser (6328 Å) and thirty one Raman bands have been recorded. The far infrared spec trum which reveals six absorptions in the 10–270 cm⁻¹ region and the infrared spectrum from 300–3200 cm⁻¹ have been observed, and correlations with the Raman frequencies have been established. Assignments of some of the characteristic frequencies have been made, and the implications of the data regarding the geometry of the molecule are discussed.     

On the structure and stability of Ar n and Ar n + clusters at finite temperature

For Ar_2–29 and Ar _2–29 ⁺ clusters at 20 K in the polarization model presented here the electrodynamical dipole-dipole many-body problem is solved selfconsistently with the Monte-Carlo method (MC) at 20 K, i.e. the instantaneous dipole-dipole interaction is solved to infinite perturbation order and in cluster expansion to the order of the cluster size. The long range many-body dipole-dipole interaction is coupled to exchange interaction by a modified effective dipole polarizability. This model will be compared to the dimer model and classical MC simulation of Ar _n . The resulting different magic numbers in the binding energies are discussed in this connection with different experimental techniques of cluster ionization. By the mean square cluster diameter a shape parameter is introduced and it is found that with this parameter structural form transition in cluster growth can be resolved, and surprisingly do not correlate with the magic numbers.     

Gaussian representations of charge overlap effects in intermolecular forces

The ground state H? H⁺ and H? H interactions are used as model interactions for investigating the feasibility of using Gaussian basis sets for representing charge overlap effects in intermolecular forces. The non-expanded charge-induced dipole energy and the non-expanded dipole-dipole dispersion energy, respectively, for these interactions are calculated using two types of Gaussian basis functions to represent the first order wave function, Ψ⁽¹⁾. Very good results for these interaction energies, which include charge overlap effects, are obtained for all interatomic separations by using small Gaussian basis sets to represent the interaction, that is Ψ⁽¹⁾, and/or the isolated atoms (the zeroth order wave function).     

Structure,vibrational assignment,normal coordinate analysis,and ab initio calculations of methylisocyanate

The infrared (3200-30 cm⁻¹) and Raman (3200-10 cm⁻¹) spectra of gaseous and solid methylisocyanate, CH3NCO, have been recorded. Additionally, the Raman spectrum of the liquid has been obtained and qualitative depolarization ratios have been measured. The CNC bend has been observed in the far infrared and low frequency Raman spectra of the gas at approximately 172 cm⁻¹. An additional far infrared band at ≈50 cm⁻¹ has tentatively been assigned as the methyl torsional mode, although it could be due to the Δν = 1, Δl = ± 1 transitions of the CNC bending mode. A complete assignment of the vibrational fundamentals is proposed. The structural parameters, force constants, and vibrational frequencies have been determined from ab initio Hartree—Fock gradient calculations using the 6-31G* basis set. Additionally, structural parameters have been obtained with the 6-311 + + G** basis set with electron correlation at the MP2 level which are compared to those obtained from the microwave data and electron diffraction study. These results are compared with the corresponding quantities obtained for similar molecules.     

过渡金属表面α-吡啶基的振动光谱学判据

基于簇模型采用密度泛函理论在B3LYP/6-311+G^**/LANL2DZ(metal)基组水平上计算了吡啶及α-吡啶基吸附于Pt、Pd、Rh、Ni四种金属表面的红外和拉曼光谱. 通过详细地分析和比较计算结果与文献报道的实验谱图, 提出了以N端吸附的吡啶分子和α-吡啶基这两种表面物种各自存在的谱学判据. 计算结果表明在以上四种金属表面, α-吡啶基的拉曼活性比吡啶的小, 而特征谱峰的红外强度与吡啶相当. 该结果表明红外光谱是检测金属表面α-吡啶基的有效手段, 也解释了采用表面增强拉曼光谱和红外光谱研究吡啶吸附在金属表面得出不同结构的原因.     

Interpretation of chromatographic retentions of simple solutes with an amylose-based sorbent using infrared spectroscopy and DFT modeling

The interactions of amylose tris(3,5-dime- thylphenylcarbamate) (ADMPC, commercially “Chiralpak AD”) with 10 simple solutes—1-propanol, heptane, heptanol, benzene, propylbenzene, benzyl alcohol, pyridine, tetrahydrofuran, diethylamine, and aniline—are studied using attenuated total reflection infrared spectroscopy (ATR-IR) of thin polymer films, DFT modeling, and high performance liquid chromatography (HPLC). ATR-IR is used to determine the changes in the hydrogen bonding states of the C=O and NH groups of the polymer amide I and II bands upon absorption of each of the solutes at 25^∘C. DFT modeling with B3LYP/6-311+g(d,p) level of theory is used to predict the IR wavenumbers, the H-bonding interaction energies, and the hydrogen bonding distances of the polymer side-chains with certain solute molecules. The capacity factors of these solutes with ADMPC have been measured at 25^∘C in hexane/isopropanol (95/5, v/v) solvent. From IR data and DFT modeling, we conclude that the C=O and NH are key binding sites of the polymer and interact with the functional groups of various solutes. The capacity factors are understood on the basis of hydrogen bonding, hydrophobic, and dipole-dipole interactions of the C=O, NH, and phenyl groups of the sorbent with OH, NH, NH₂, O, phenyl, and N functional groups of the solutes.     

The vibrational spectra of maleimide and N-D maleimide

The infrared spectra of maleimide as a vapour (160°C), melt (100°C), oriented polycrystalline film, pellet and when dissolved in various solvents were recorded between 4000 and 400 cm^?1. Also certain spectra in the far infrared region 400-40 cm^?1 were obtained. Raman spectra of the crystalline solid, melt and as a saturated solution in acetonitrile were recorded and semiquantitative polarization measurements carried out. For N-D maleimide infrared and Raman spectra of the solid compound were recorded.The fundamental frequencies have been assigned in terms of C_2v, symmetry on the basis of infrared vapour contours and dichroism of the oriented film as well as on Raman polarization data. A force field was derived for maleimide, by initially transferring force constants from maleic anhydride and subsequent refinement of the force constants. The agreement between observed and calculated frequencies for the in-plane modes was satisfactory whereas certain large discrepancies remained for the out-of-plane vibrations.     

Far-infrared and Raman study of lithium and sodium cryptates in nonaqueous solvents

Far-infrared spectra of sodium and lithium cryptates were observed in several nonaqueous solvents. The spectra are characterized by a broad band whose frequency is independent of the solvent or of the anion and which is assigned to the vibration of the cation in the cryptand cavity. The band frequencies were 234±2, 218±1, 243±3, and 348±1 cm^?1 for Na⁺-C222, Na⁺-C221, Li⁺-C221, and Li⁺-C211 cryptates, respectively. These bands were found to be Raman-inactive, indicating that the cation-ligand interaction is very largely electrostatic in nature.     

Some observations on the NOE effect in 1H NMR spectroscopy

The NOE enhancement factor in ¹H NMR spectroscopy is shown to be a function of dipole-dipole interaction of the solute. The NOE increases with increasing concentration if a monomer-dimer equilibrium exists in solution.     

Far infrared spectrum of crystalline carbon disulphide

The far infrared spectrum of crystalline carbon disulphide has been measured at about 1.8 K. Two absorption bands are observed, with maxima at 66.5 and 68.2 cm^?1, respectively, and with nearly equal intensities. They are considered to be due to the two infrared active translational modes expected by lattice dynamics.     

Nuclear magnetic resonance investigation of thallium-205 ion adsorbed on hydrated silica

The relaxation mechanism of ²⁰⁵Tl⁺ adsorbed on hydrated silica is controlled by the nuclear dipole-dipole interaction. The correlation time is estimated to be equal to about 3 × 10^?9 s. The thallium-205 resonance is up-field shifted by 80 ppm as compared to the free solution.     

Ab initio calculations of doubly resonant sum-frequency generation second-order polarizabilities of LiH

In the present Letter doubly resonant sum-frequency generation (DR-SFG) second-order polarizabilities (β) are reported for the lithium hydride molecule. The calculations, which refer to the diagonal longitudinal component of β and ignore rotation, are based on data evaluated using the multireference configuration interaction method with singles and doubles. The DR-SFG results are partitioned into their infrared–visible and visible–infrared components. They are analyzed as a function of the infrared and visible frequencies as well as the number of vibrational states considered in the sum-over-states expressions.