276-nm absorption band system of m-dichlorobenzene: Rotational band contour analysis

The 276-nm absorption band system (${}^1\text{B}{}_2\text{←}{}^1\text{A}{}_1$) of m-dichlorobenzene was photographed under high resolution. The electronic origin band (0, 0) and a band at (0 + 380) cm^?1 were subjected to rotational “band contour” analysis. As a result, it is found that the origin band has a type A band contour and that at (0 + 380) cm^?1 exhibits a type B band contour. The band contour analysis also yields an accurate determination of the excited state parameters, viz., A′ = 0.0911 ± 0.0003, B′ = 0.02852 ± 0.00005, and C′ = 0.02175 ± 0.00001 cm^?1. A model geometry for the molecule m-DCB in its first excited singlet state has been proposed.     

The 341 nm band system of pyridine-N-oxide. Analysis of the in-plane vibrational structure

The near-ultraviolet absorption of pyridine-N-oxide has been photographed at high resolution in the range 295–365 nm, and a weak, long-axis polarized subsystem of A-type bands has been identified in the spectrum for the first time. The presence of both A- and B-type bands in the system establishes conclusively that the transition is $\text{π}{}^1\text{← π [}{}^1\text{B}{}_2\text{←}{}^1\text{A}{}_1\text{]}$.The complete set of a₁ and b₂ fundamental frequencies has been identified in the ground and excited states of the transition, using infrared and Raman measurements to supplement the data from the electronic analysis. Physical structure in the excited state has not been determined but appears qualitatively to involve a generalized increase in the dimensions of the ring, coupled with a decrease in the NO distance. The structure of the band system is very similar to that of isovalent aromatic molecules, including phenol and chlorobenzene.     

276-nm absorption band system of m-dichlorobenzene: Vibrational fine structure analysis

The vibrational fine structure accompanying the 276-nm absorption band system (${}^1\text{B}{}_2\text{←}{}^1\text{A}{}_1$) of m-dichlorobenzene (m-DCB) vapor has been reanalyzed. Unambiguous assignments for about 80% of the measured transitions have been presented here. The assignments have been greatly facilitated by the results of band contour analysis as well as Raman and ir data. Vibrational fine structure assignments have led to a determination of excited state fundamentals which are not allowed to appear in single quantum excitation. Wherever possible, a close correspondence has been established between the various normal modes of m-DCB and benzene.     

The symmetric amino-wagging band of hydrazine: Assignment and analysis

For the first time a weak fundamental symmetric amino-wagging band, ν₆, was assigned in the high-resolution Fourier-transform infrared spectrum of hydrazine. The analysis of the Fermi-type resonance between the ν₆ and the third excited torsional state, 3ν₇, is presented. A global fitting was carried out taking into account 3392 lines of the ν₆ band (for K′ from 0 to 10 and for all symmetry species) and 428 lines of the 3ν₇ band (for K′ from 3 to 9 and only for the symmetry species in resonance). For all 3820 rovibrational transitions the overall standard deviation of the fit of 0.019 cm⁻¹ was obtained. The band centers of the symmetric wagging state and the third torsional were determined at 795.137 and 860.138 cm⁻¹, respectively. Individual fits were also carried out for K′ from 3 to 8 for all symmetry species with much improved standard deviations. The effective group-theoretical Hamiltonian for the coupling between inversion and torsion states was used.     

Theoretical prediction of vibrational spectra: The out-of-plane force field and vibrational spectra of pyridine

The harmonic force field for the out-of-plane vibrations of pyridine has been calculated from ab initio Hartree-Fock wavefunctions obtained with a 4–21 basis set of contracted Gaussians. To account for systematic errors, the calculated force constants were scaled, using only two independent sclae factors which were transferred unchanged from benzene. The resulting scaled quantum mechanical force field, which is strictly a priori in that it is not based on any experimental data on pyridine, predicts the 64 out-of-plane fundamental frequencies of pyridine and its deuterated isotopomers of C_2v symmetry with a mean deviation from experiment of only 8.5 cm^?1. Addition of polarization functions to the basis set for the nitrogen atom and refinement of the two scale factors by fitting them to the observed pyridine spectra produce no significant improvement in the fit. Assignments of the vibrational spectra are discussed.     

Optically pumped molecular-iodine laser on the 342-nm band

Lasing of molecular iodine has been observed on 342-nm band system. The laser was produced with optical pumping by the radiation of high-current discharge mixtures of iodine vapour, sulfur hexafluoride and argon. The highest energy output 0.4 J in a 5 μs pulse corresponding to the specific laser energy of ～10^-3 J/cm³ has been obtained.     

The 404.5-nm system of the ReO molecule

Observations on the emission spectrum of ReO in the region 375–870 nm are reported. Five bands of a $\text{ΔΩ}\text{= 0}$ system with (0, 0) band at 404.5 nm have been rotationally analyzed and the principal results for ¹⁸⁷ReO are (in cm^?1) ν₀ = 24 709.90, B′_e = 0.3819, B″_e = 0.4252, ω′_e = 874.8₂, and $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 979.1}{}_2$. Data on the minor isotopic species ¹⁸⁵ReO are also reported. It is suggested that broad rotational profiles found in bands near 842 nm may be due to nuclear hyperfine structure.     

The 275-nm absorption system of anisole

The 275-nm absorption systems of anisole (methoxybenzene) and three deuterated derivatives have been photographed at medium to high resolution. The origin bands lie at 36 386.4, 36 389.6, 36 557.2, and 36 560.4 cm^?1 for C₆H₅OCH₃, C₆H₅OCD₃, C₆D₅OCH₃, and C₆D₅OCD₃. The vibrational structure, which was analyzed in some detail, was found to be very similar to that of the analogous system of phenol. The spectrum consists of both allowed and forbidden components although the forbidden component, principally evident through activity of vibrations 18b and 6b, is relatively weak.     

The 280-nm absorption system of benzoyl fluoride

Benzoyl fluoride exhibits a weak, discrete absorption system in the region 290 – 260 nm. Vibrational structure associated with the C₆H₅COF and C₆D₅COF isotopes has been analyzed in detail. The C₆H₅COF and C₆D₅COF origin bands lie at 35 685 and 35 829 cm^?1, respectively. The intensity in the spectrum is principally associated with two progressions, ν′₁₉, the breathing vibration of the benzene ring and ν′₂₄, a COF in-plane bend, and sequence bands involving the COF torsion motion ν₃₆. The $\text{C}{}_6\text{H}{}_5\text{COF}\text{C}{}_6\text{D}{}_5\text{COF}$ν₁₉, ν₂₄, and ν₃₆ vibrational frequencies are respectively 1005/-, $\text{376}\text{357}\text{,}\text{and}\text{57}\text{55}\text{cm}{}^{\mathrm{?1}}$ in the ground state and $\text{950}\text{919}\text{,}\text{348}\text{331}\text{,}\text{and}\text{89}\text{85}\text{cm}{}^{\mathrm{?1}}$ in the excited state. The barriers to rotation of the COF group are estimated from the torsional frequency data to be 1450 and 3450 cm^?1 in the ground and excited electronic states, respectively.     

The 290-nm absorption system of propiolyl fluoride

The vapor-phase absorption spectrum of propiolyl fluoride HCCCOF and deuterio-propiolyl fluoride has been examined under medium resolution in the region from 303 to 260 nm. While considerable vibrational structure is evident, all bands are found to be rotationally diffuse. The electronic transition is identified as the singlet-singlet $\text{π}{}^1\text{← n}$ transition analogous to the 382-nm system of propynal. The evidence for a nonplanar excited-state geometry is discussed. The principal excited-state vibrational frequencies identified are 158 (ν′₉), 396 (ν′₈), and 1222 cm^?1 (ν′₃) for HCCCOF. The corresponding values for DCCCOF are 150, 390, and 1217 cm^?1, respectively. The triplet ← singlet system involving the same electron promotion has not been found.     

Dielectric properties of pyridine N-oxide aqueous solution under the static electric field and microwave field

Molecular dynamics simulations of the pyridine N-oxide aqueous solution have been performed in the canonical ensemble macroscopic canonical ensemble (NVT) both in the absence and presence of an external electromagnetic field. It extracts the radial distribution function for each concentration solution, dielectric constant and other information on dielectric properties. Analysing the microscopic dielectric information of the aqueous solution under the static electric field (0–3×10⁹ V/m) and microwave frequencies (2.45G, 0–3×10⁹ V/m), and comparing the dielectric information between the different concentrations and different field strengths, we can get the dielectric properties of two kinds of polar aqueous solution under microwave irradiation. Thus, this project can provide the data of the sample to other correlation studies.     

Selenium dioxide: Analysis of the 419-nm absorption system

The C absorption systems in the region 370–500 nm of the three isotopic species ⁷⁸Se¹⁶O₂, ⁸⁰Se¹⁶O₂, and ⁷⁸Se¹⁸O₂ have been comparatively studied in the vapor phase. The 0₀⁰ band is at 23840, 23840, and 23842 cm^?1, respectively. The vibrational structure consists of long progressions in the bending mode ν′₂(a₁) ～ 200 cm^?1, which are based on the origin band and on vibronic origins in which all three normal modes can be active. Most bands are severely overlapped, so that detailed rotational analyses are not possible. Band contour analysis of the 2₀²3₁⁰ band indicates that the transition is ${}^3\text{B}{}_2\text{-}\text{X}\text{?}{}^1\text{A}{}_1$, which acquires intensity by both spin-orbit and spin-vibronic coupling mechanisms. The estimated bond length and angle in the triplet state are 1.69 Å and 100°, respectively, the latter representing a large decrease from the ground state value of 114°.     

Tunable out-of-plane band gap of two-dimensional anisotropic photonic crystals infiltrated with liquid crystals

We analyze the tunability of out-of-plane band gap in two-dimensional photonic crystals created by square and triangular lattices of air holes in anisotropic tellurium background, considering that the rods are infiltrated with liquid crystal. Using the plane wave expansion method, we study the variation of out-of-plane band gap by changing the optical axis orientation of liquid crystal.     

The 2644-Å band system of fluorobenzene. The cold band spectrum

The 2644-Å band system of fluorobenzene and two deuterated isotopes has been photographed and a vibrational analysis proposed. The present paper is limited to the cold band spectrum. Three major Fermi resonances in the normal isotope are discussed and several other confusing aspects of the spectra are resolved. The present analysis has led to a successful assignment of some 80% of all measured transitions. The analysis is strengthened by the homology among the isotopes and consistency with some related fluorobenzene studies is maintained.     

The band spectrum of SbO: A new doublet system

The band spectrum of SbO was excited in a heavy current discharge from a 2000 volt D. C. generator. A new doublet system of bands occurring in the region λ 2800 toλ 3600 arising from a transition of the type²Δ_r?² Π _r was identified. The lower² Π _r state is found to be common to those of the three band systems reported earlier, which is in all probability the ground state of the SbO molecule. The band heads of the high frequency and low frequency components could be represented by the following quantum formulae:

$$\begin{gathered} ^2 \Delta _{\tfrac{3}{2}} - ^2 \Pi _{\tfrac{1}{2}} : \hfill \\ v = 29754 \cdot 6 + 570 \cdot 6 (v' + \tfrac{1}{2}) - 3 \cdot 52 (v' + \tfrac{1}{2})^2 - 820 \cdot 5 (v'' + \tfrac{1}{2}) + 4 \cdot 62 (v'' + \tfrac{1}{2})^2 \hfill \\ ^2 \Delta _{\tfrac{5}{2}} - ^2 \Pi _{\tfrac{3}{2}} : \hfill \\ v = 28044 \cdot 8 + 568 \cdot 1 (v' + \tfrac{1}{2}) - 3 \cdot 28 (v' + \tfrac{1}{2})^2 - 819 \cdot 2 (v'' + \tfrac{1}{2}) + 4 \cdot 62 (v'' + \tfrac{1}{2})^2 . \hfill \\ \end{gathered} $$     

Electronic spectrum of acetaldehyde: Vibrational analysis of the 182-nm system

The electronic absorption spectra of CH₃CHO, CH₃CDO, CD₃CHO, and CD₃CDO have been obtained in the vacuum ultraviolet region. Vibrational analysis of the 182-nm system was made with the help of wavenumbers from their infrared spectra and also geometries and wavenumbers obtained from ab initio calculations. This system is assigned as a single Rydberg (3s ? n) electronic transition.     

Pair association and complexation with water of matrix-isolated pyridine N-oxide: A theoretical study of their manifestations in the IR spectrum

The structure and the IR spectra of three types of pair associates of pyridine N-oxide, as well as of three different complexes of this compound with one or two water molecules, are calculated in terms of the supramolecular approach by the B3LYP/6-311+G(d, p) hybrid density functional method. The experimentally observed IR spectrum of pyridine N-oxide in a low-temperature Ar matrix is theoretically interpreted in detail. The agreement in sign and magnitude between all the calculated and observed frequency shifts of fundamental vibrations shows that the hydrogen-bonded complexes make the main contribution to the formation of complex bands of self-associates.