Assignment of the microwave spectrum of trioxane in the v19(E) = v20E) = 1 state

An analysis of the rotational spectrum associated with two degenerate states simultaneously excited by one quantum is carried out for the first time for symmetric top molecules. The microwave spectrum of trioxane in the v₁₉(E) = v₂₀(E) = 1 state has been measured in the range 60–145 GHz and assigned using a graphical method. Accurate molecular parameters are determined by diagonalization of the energy matrices obtained by factoring the matrix constructed using the eigenvectors of the zeroth-order Hamiltonian as a basis.     

An AB3 high-resolution NMR spectrum in the solid state: 31P in P4S3

A high-resolution ³¹P NMR spectrum has been recorded in polycyrstalline tetraphosphorus trisulphide P₄S₃. The spectrum exhibits the resolved doublet and quartet structure characteristic of an AB₃ type spectrum, with chemical shift difference 185 ± 2 ppm and J = 70 ± 3 Hz.     

Optical spectroscopic studies of the polymerization of (SN)on radicals to (SN)x in thin films

Optical absorption measurements between 300 and 50000 cm^?1 in the 12 to 300 K temperature range, on thin films of (SN)^o_n radicals deposited from (SN)_x vapors, are presented. The spectrum of a thin film deposited at 12 K is interpreted as arising from the SN vibrational modes and electronic transitions of the ring S₄N₄ molecule, the linear (SN)^o_x radical and an (SN)^o_n radical longer chain length. The temperature induced evolution of the optical spectrum and the probable nature of the polymerized blue—black films, shown by preliminary X-ray data to be non-crystalline, are discussed.     

Laser excited S2 → S1 and S1 → S0 emission spectra and the S2 → Sn absorption spectrum of azulene in solution

We present the S₁ → S₀ fluorescence spectrum, between 740 and 940 nm, of azulene solutions (10^?3 M in methanol) excited with a Q-switched ruby laser. The nitrogen-laser excited S₂ → S₁ fluorescence spectrum, between 700 and 930 nm, is also reported. The transient S₁ → S_n spectrum between 500 and 650 nm was studied, using synchronous nitrogen laser and dye laser excitation. The S₅ (¹B₁(3)) state of azulene was found to be located at 45500 cm^?1 and the cross section σ₂₅ of the transient absorption S₂ → S₅ is estimated to be 3 × 10^?18 cm²/molecule.     

Microwave spectrum and substitutional structure of CH2DF

Forty-two transitions of the microwave spectrum of CH₂DF have been observed in the region between 75 and 450 GHz. The measurement of both a-type and b-type transitions makes possible the analysis of the spectrum and the accurate calculation of the rotational constants (in MHz): = 119 675.0535 ± 0.074, = 24 043.4415 ± 0.072, ? = 22959.3732 °0.072, °j = 0.049371 ±0.00011, °_jk = 0.34268 ±0.0006, 2_k = 3,3774 ± 0.0035, δ _j = 0.002329 ± 0.000045, δ_k = 0.0687 ± 0.036. These constants, in combination with the results of earlier work on the symmetric speci r_s structure calculation based entirely on high-accuracy microwave data. The structural parameters are r_CH = 1.100 Å, r_CF = 1.383 Å, and ∠HCH = 110° 37'.     

Multiphoton ionisation spectroscopy of H2S: a reinvestigation of the 1B1-1A1 band at 139.1 nm

The 3 + 1 multiphoton ionisation (MPI) spectrum of the ¹B₁-¹A₁ transition in H₂S at 139.1 nm has been recorded in both linearly and circularly polarised light. The rotational structure shows marked differences from that of the one-photon absorption spectrum. Properties of the excited state revealed through analysis of this structure include confirmation of its ¹B₁ character, refined values for its A, B and C rotational constants and the operation of an energy-dependent predissociation mechanism. It is shown that the third-rank tensor component of the transition operator dominates over the first-rank component in this MPI band. The orbital nature of this ¹B₁ excited state is considered.     

Revised analysis of the structure of the v1 band of methane

The CARS spectrum of the v₁ band of ₁₂CH₄ at a pressure of 14 mbar was recorded using cw excitation in the cavity of a ring argon ion laser. The analysis of the intensity profile of the obarred spectrum led to the detection of inconsistencies with the hitherto proposed calculated positions of transitions with J = 7 to J = 10 and to a relocation of the corresponding lines.     

The SO+2 radical-ion

From the complex overall EPR spectrum of ⁶⁰Co gamma-irradiated pure solid sulfur dioxide the spectrum of the SO⁺₂ radical-ion was selected and the following principal values for the g-tensor obtained: g₁ = 1.9620;g₂ = 2.0026;g₃ = 2.0118 (Δg = ± 0.0005).     

A study of the spinel materials LiTi2O4 and Li43Ti53O4 by photoelectron spectroscopy

HeI-excited valence-band ultraviolet photoelectron spectra and MgKα-excited Ti-2p X-ray photoelectron spectra are reported for the spinel materials LiTi₂O₄ and $\text{Li}{}_{\mathrm{<mtext>4</mtext><mtext>3</mtext>}}\text{Ti}{}_{\mathrm{<mtext>5</mtext><mtext>3</mtext>}}\text{O}{}_4$. The presence of a Fermi edge in the ultraviolet photoelectron spectrum of LiTi₂O₄ confirms the metallic nature of this material, although the measured density of states at the Fermi energy is much lower than that expected from an independent-electron interpretation of the magnetic susceptibility. This difference is attributed to a strong interaction of the conduction electrons with the lattice vibrations. The localization of conduction electrons that occurs in the final state in the Ti-2p X-ray photoelectron spectrum of LiTi₂O₄ is attributed to a Coulomb interaction with a core hole.     

Theoretical calculation of the electronic structure and the optical spectrum of CrF2−6

The electronic structure of the CrF^2?₆ cluster has been analyzed by solving the Hartree-Fock equations on several electronic states, at five values of R, the metal-ligand distance in the a_1g vibration. The methodology of J. W. Richardson, T. F. Soules, D. M. Vaugth, and R. R. Powell (Phys. Rev. B4, 1721 (1971)) has been used. The computed R_e is in close agreement with the observed value in alkali hexafluorochromates(IV). The nuclear potentials of the d² triplets are almost parallel to the ground state potential, giving rise to a weak R-dependence of the spin-allowed transitions and a negligible contribution of the a_1g progression to the vibrational structure of the broad bands. The absorption spectrum has been discussed in terms of the results of different SCF calculations. A new assignment is proposed that avoids most of the earlier difficulties of the spectral interpretation. The best calculated spectrum agrees with the one observed in Rb₂CrF₆ within 1.5 kK.     

Electronic transitions in Li4CoCl4.10H2O

The electronic spectrum of Li₄CoCl₆.10H₂O was recorded at liquid nitrogen temperature in the 4,000–25,000 cm^?1 spectral region. The simi larity of this spectrum to that of CoCl₂ permitted us to assume O_h syn metry of the [CoCl₆]^4? cluster in our sample. The band assignment was performed in the crystal field approximation using Tanabe and Sugano's energy matrices for Dq = 730 cm^?1, B = 820 cm^?1 and C/B = 4.4.The large number of bands and high intensity of the maxima in the regio 19,000–21,000 cm^?1 is discussed.     

Matrix isolation study of the vacuum ultraviolet photolysis of allene and methylacetylene. Vibrational and electronic spectra of the species C3, C3H,C3H2, and C3H3

Upon hydrogen-discharge photolysis of normal or deuterium-substituted allene or methylacetylene in an argon or a nitrogen matrix at 14°K, infrared absorptions of all of the C₃H_n species with n < 4 appear. A hydrogen-deformation fundamental of C₃H₂ has been identified in the far infrared. Infrared studies of the partially deuterium- substituted methylacetylenes indicate that extensive photoisomerization occurs. The observed products are consistent with those predicted using the previously postulated gas-phase photolysis mechanism. The ultraviolet spectrum of C₃H₃ corresponds closely with that characteristic of the gas-phase molecule. Comparison of the spectrum between 1900 and 4000 A of photolyzed methylacetylene with that of matrix-isolated graphite vapor has indicated that any new electronic transition of C₃ in this region must be weak.     

A layered vanadium arsenate network decorated with the directly coordinated organonitrogen ligands: [V4O7(HAsO4)2(o-phen)2] (o-phen=o-phenanthroline)

A novel layered vanadium arsenate [V₄O₇(HAsO₄)₂(o-phen)₂] 1 (o-phen=o-phenanthroline) was synthesized by the hydrothermal reaction of V₂O₅, ZnCl₂, Na₂HAsO₄·7H₂O, o-phenanthroline (o-phen) and water. Its structure was determined by elemental analyses, ESR spectrum, XPS spectrum, TG analysis, IR spectrum and the single-crystal X-ray diffraction. Compound 1 crystallizes in monoclinic system, space group P2/c, a=10.122(2) Å, b=9.867(2) Å, c=15.367(3) Å, β=102.83(3)°, V=1496.4(5) Å³, Z=1, λ(MoKα)=0.71073 Å, (R(F)=0.0397 for 3422 reflections). Data were collected on a Rigaku R-AXIS RAPID IP diffractometer at 293 K in the range of 2.06°<θ<27.48°. The title compound contains an unusual two-dimensional (2D) As-V-O layer with four-, six- and eight-membered rings. The chelating o-phen ligands project perpendicularly above and below the undulating layer. 1 represents the first example of 2D inorganic vanadium arsenate backbone grafted with the directly coordinated organic ligands. Furthermore, the 3D supermolecular architecture is formed by π-π stacking interactions of the o-phen groups between adjacent layers.     

Properties of the ammonium tartrate/EPR dosimeter

The EPR response of γ-irradiated ammonium tartrate on the absorbed dose of γ-rays up to 22 kGy as well as the changes in the shape of the EPR spectrum upon applied modulation amplitude and microwave power are reported. Also the possibility to use ammonium tartrate together with Mn²⁺ magnetically diluted in MgO as an internal reference material is evaluated. The influence of the microwave power and the modulation amplitude on their dose response is investigated. The results show that the radiation-induced EPR spectrum of ammonium tartrate, obtained at a low microwave power is complex consisting several patterns and is more easily saturated than the Mn²⁺ EPR spectrum. In this case the following settings of the EPR parameters are recommended: H_mod⩽0.05 mT and 10⩽P_MW⩽13 mW. Using these parameters the dosimeters can be considered for use in intercomparisons.     

Synthesis, characterization of TiO2 nanotubes-supported MS (TiO2NTs@MS, M=Cd, Zn) and their photocatalytic activity

TiO₂ nanotubes-supported MS (TiO₂NTs@MS, M=Cd, Zn) are synthesized by a simple wet chemical method at room temperature. The products are characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis absorption spectrum and photoluminescence (PL) spectrum. Their optical and morphological properties indicate the interaction between the TiO₂ nanotube and MS nanoparticle. The photocatalytic activities of the TiO₂NTs@MS are evaluated upon the oxidation of methyl orange under UV light illumination. The results reveal that the photocatalytic efficiency of the nanocomposites strongly depends on the specific interaction between MS and support.     

Analysis of the absorption and magnetic circular dichroism spectra of the hypertensive band in (h5C5H5)Ho(h8C8H8)

The solution MCD spectrum of (h⁵C₅H₅)Ho(III)(h⁸C₈H₈) is dominated by C terms but displays distinct A term under the hypersensitive ⁵I₈ — ⁵G₆ transition. Intermediate field analysis suggests this transition originates from the first electronic excited state and is enhanced by τ cyclopentadienyl ligand polarization.     

Spectroscopic properties of Ln2MoO6:Eu3+

The spectroscopic properties of Ln₂MoO₆:Eu³⁺ (Ln = La, Gd, Y) compounds were investigated. The differences in the recorded fluorescence spectra are in accord with the different structures. For the La₂MoO₆:Eu³⁺ case, the spectrum is compatible with a C₂ point site symmetry. It appears that the energy level scheme is connected with the rare earth oxychloride one, so it is possible to determine accurately sets of crystal field parameters simulating the spectrum. For the other compounds, the Eu³⁺ ions occupy three different point sites. By using the site-selective excitation on the ⁵D₀ level it is possible to identify the energy level scheme characterizing each point site.     

Two-photon spectroscopy in the gas phase: 1B2u ← 1Ag transition of p-difluorobenzene

The two-photon excitation spectrum ¹B_2u ← ¹A_g of p-difluorobenzene in the gas phase is presented and analysed. The normal absorption is electric dipole allowed and shows no vibronic coupling, but the two-photon absorption is electric dipole forbidden and displays rich vibronic structure. Eight vibronic origins are assigned to their excited state fundamentals by analysis of the hot bands and by analogy with benzene. The only previously unassigned ground state frequency, an a_u mode, is active in the spectrum and is accordingly assigned. The sequences and the abundant Fermi resonances accompanying absorption are also partially assigned.     

Spectroscopic and structural characterization of Na2[(VO)2(ttha)]·8H2O (ttha = triethylenetetraamine-N,N,N′,N″,N′″,N′″-hexaacetate): Interpreting the results with density functional theory

Na₂[(V^IVO)₂(ttha)]·8 H₂O (ttha = triethylenetetraamine–N,N,N′,N″,N′″,N′″–hexaacetate ion), prepared by treating [VO(H₂O)₅][(VO)₂(ttha)]·4 H₂O with Na₆(ttha), has been characterized by single crystal X-ray diffraction, infrared spectroscopy, UV–Vis absorption spectroscopy, electron spin resonance spectroscopy, and modeled by density functional theory (DFT). The X-ray structure revealed a distorted octahedral geometry around each vanadium center. The electronic absorption spectrum of [(VO)₂(ttha)]²⁻ (aq) features absorptions at ca. 200 nm (ε > 13900 L mol⁻¹ cm⁻¹), 255 nm (ε = 3480 L mol⁻¹ cm⁻¹), 586 nm (ε = 33 L mol⁻¹ cm⁻¹), and 770 nm (ε = 38 L mol⁻¹ cm⁻¹). The time-dependent density functional theory (TDDFT) calculated electronic absorption spectrum was remarkably similar to the actual spectrum, and TDDFT predicts absorption peaks at 297, 330, 458, 656, and 798 nm. TDDFT assigned the peak at 798 nm to be the α spin HOMO → LUMO transition. Hence, the peak at 770 nm in the actual spectrum is most likely the α spin HOMO → LUMO transition. Moreover, the TDDFT calculations revealed that the α spin HOMO and LUMO are partly comprised of d orbitals on both vanadium centers, and the first derivative electron spin resonance spectrum also suggests that the two unpaired electrons in [(VO)₂(ttha)]²⁻ are localized near the vanadium centers.     

Location of the first 3B2 ← 3B+2 transition in phenanthrene

The polarization of the triplet-triplet absorption spectrum of phenanthrene-d₁₀ in the region from 3500 to 8500 A has been recorded. The ³B₂^? state is located at about 4250 Å. The possibility that phenanthrene might be a suitable chromophore for laser dye synthesis is discussed.