The near ultra-violet absorption spectrum of tropolone vapour

A vibrational analysis of the 370 nm system of tropolone (-OH) and (-OD) has shown that pairs of bands, resembling the O₀ ⁰ and H₁ ¹ bands (where v _H is the internal hydrogen-bonding vibration), dominate the spectrum. Pairs built on O₀ ⁰ and H₁ ¹ and due to the excitation of totally symmetric vibrations in the ground or excited electronic state are well-behaved in the sense that their separations and rotational contours are very similar to those of O₀ ⁰ and H₁ ¹. About seven sequence intervals, in vibrations other than v _H, have also been identified and it is observed that rotational contours of Z₁ ¹H₁ ¹ bands in five sequence-forming vibrations Z are quite strongly perturbed (four of them in a very similar way) while the corresponding Z₁ ¹ bands are unperturbed.

It is concluded that the unusual nature of v _H is in some way responsible for the rotational perturbations and also for the very unusual behaviour of some quite intense vibronic bands in the region 290–540 cm^-1 to high wavenumber of the O₀ ⁰ band: however, the evidence is only circumstantial.     

Electronic spectra of chromate doped 3CdSO4 · 8H2O crystals

The optical absorption spectra of CrO^2-₄ doped 3CdSO₄ · 8H₂O crystals revealed four bands. The two prominent bands at 27, 030 and 36, 360cm^-1 along with the featureless, intense band at 41, 670cm^-1 are assigned to the electronic transition ¹A₁→¹T₂. The lowest energy band at 24,100 cm^-1 is attributed to the orbitally forbidden transition ¹A₁→¹T₁ in accordance with the Molecular Orbital scheme of Viste ang Gray. The spectrum recorded at 80 K exhibited a fine structure superposed on the two prominent bands. The structure is ascribed to the vibrational progression of totally symmetric breathing mode in CrO^2-₄ ion.     

Symmetric linewidth variations in the electron resonance spectra of biradicals

The infrared emission spectrum of the Rydberg molecule XeH was recorded with the Kitt Peak Fourier transform spectrometer. XeH was made in a hollow cathode discharge of 2·2 torr H₂ and 0·1 torr Xe. The 0-0 bands of the C ²Π-B ²Σ⁺ and the D ²Σ⁺-C ²Π transitions were observed near 3250 cm^?1 and 4420 cm^?1, respectively. A rotational analysis provides spectroscopic constants for these states.     

High-Resolution Fourier Transform Infrared Spectrum of the ν1+ν3 Band System of HCCH

A high-resolution vibration-rotation overtone spectrum of H¹³C¹²CH has been recorded with a Fourier transform infrared spectrometer in the wavenumber region 6400 to 6700 cm⁻¹. The main band, assigned as the C-H stretching combination band ν₁+ν₃, and some overtone and hot bands have been rotationally analyzed. Altogether eight parallel bands have been observed. The vibrational labels have been deduced on the basis of the assignments of the fundamental ν₃ antisymmetric C-H stretching band system.     

The A2Σ+-X2Πi electronic band system of the OD free radical: Spectroscopic data for the 0-0 sequence,and rotational term values for A2Σ+ and X2Πi

The A²Σ⁺-X²Π_i emission system of the OD radical has been recorded at high resolution from a discharge through flowing D₂O at 0.1 torr pressure. The 0-0, 1-1, and 2-2 bands of the Δv = 0 sequence have been analyzed in detail for the first time. A table of the vacuum wavenumbers and wavelengths in air of the rotational lines of these bands is presented, together with some additional measurements for the 0–1 band. The data are used to obtain a self-consistent set of term values for v′ and v″ = 0, 1, which reproduces the observed line frequencies with an average deviation of less than 0.02 cm^?1. Earlier, lower resolution data for bands with v′ and v″ = 2, 3 are also combined with the present measurements to give approximate term values for these higher levels.     

Electronic photodissociation spectra of the Arn-C4H2 (n=1-4) weakly bound cationic complexes

Electronic spectra of a series of weakly bound clusters consisting of argon (Ar_n, n=1-4) bound to the butadiyne cation, C₄H₂⁺, have been recorded in the visible range from 440 to 520 nm by photodissociation. The C₄H₂⁺ fragment signal was recorded as a function of the laser wavelength during excitation of the A←X electronic transition. The observed transitions were assigned to the band origin of the cationic complexes and to vibronic bands involving excitation of the ν₃ and ν₇ vibrational modes of the C₄H₂⁺ moiety, as well as combination bands of these modes. Comparison of the photodissociation spectra of the various clusters reveals a small blue shift, 25 cm⁻¹ of the band maxima relative to the corresponding transitions reported from gas phase spectra of the bare C₄H₂⁺ cation. The magnitude of the blue shift of each band increases with successive Ar solvation up to n=3. Furthermore, each band becomes increasingly broadened towards the red with the addition of Ar atoms due to an increasing number of unresolved transitions involving excited intermolecular modes.     

Computer Resolution and Franck-Condon Analysis of the Electronic Absorption Spectrum of KMnO4 in Water

Abstract

The electronic absorptíon spectrum of KMnO₄ in water solution was analyzed. The spectral contour was resolved into component bands and then Franck-Condon approach was applied. In the investigated range of 13000–48000 cm^?1 a presence of three structureless and of two vibronic strong bands was stated. The change in the Mn-O equilibrium bond length was found to be 10.5pm for 2e·1t₁ transition (vibronic band about 18000cm^?1) and to be 16pm for the 2e·3t₂ transition (vibronic band about. 30000cm_?1). The appropriate wavenumber of the vibrational mode in these excited electronic states was found to be 735cm^?1 and about 780cm^?1, respectively. The ground electronic state wavenumber of the totally symmetric vibrational mode was fitted to be equal to 828cm^?1. Details of the proposed method of computer elaboration of electronic spectra with vibrational structure were discussed.

Electronic absorption spectra of some inorganic comppunds consist of a number of strongly overlapped bands due to their vibronic structure.^1–5 A detailed analysis of spectral contours of such compounds provides some useful information about their structure in both ground excited electronic states.

The electronic spectrum of permanganate ion is the typical example of vibronic spectra.¹ The main part of the past works based on the analysis of permanganate ion spectra in low temperatures and different polarizations. In such conditions the vibronic structure is rather good resolved and can be effectively studies.^1,3,6 Spectra of solutions as a rule are relatively poor resolved so their analysis has to be more sophisticated.

The main purpose of this work is a presentation of a new computer method for an effective study of vibronic spectra of solutions. This method has been applied to the electronic absorption spectrum of KMnO₄ in water. The method allowed us to fit the geometric parameters of spectral contour, to establish the origins and parameters of two progressions in the UV/VIS range as well as to calculate the changes in the Mn-0 equilibrium bond lengths and vibrational energy resulting from the electronic excitations of the soluted permanganate ion.     

The spectra and structure of indium iodide: The rotational and vibrational constants of the A0 state

The rotational constants of the A0⁺ state of InI are reported for the first time as B_e = 0.038077 cm⁻¹ and α_e = 0.0002373 cm⁻¹, while T_e = 24402.91 cm⁻¹ for the A0⁺-X0⁺ transition. Accurate vibrational constants for both the A0⁺ and X0⁺ states are computed from the derived band origins.     

A new electronic transition of antimony chloride in the visible region

The emission spectrum of SbCl has been photographed at high resolution in the region 400 to 640 nm. In addition to bands of two previously reported transitions in this region, A₁-X and A₂-X, 36 bands of a new system have been identified. A vibrational analysis has been made with ν₀₀ ≈ 20 679 cm⁻¹, and 7 of the bands have been rotationally analyzed. The electronic transition has ΔΩ = 0 with lower state constants which match published data for the ground state X³Σ⁻(0⁺). The upper state is characterized by the following ¹²¹Sb³⁵Cl molecular parameters: B′₀ = 0.0922 cm⁻¹, D′₀ = 3.1 × 10⁻⁸ cm⁻¹.     

Theoretical determination of the vibrational levels of NH+ 3 and its isotopomers

The vibrational levels associated with the electronic ground state X²A₂″ of NH⁺ ₃ have been determined up to 5000 cm^?1 by perturbation and variational calculations with full dimensionality of the molecule. For the variational part a new version of MULTIMODE was used which uses the ab initio electronic energy and its first derivative to define the potential energy function. These quantities were generated by the B97-1 density functional and RCCSD(T) approaches. For ND⁺ ₃, ND₂H⁺ and NDH⁺ ₂ the vibrational levels were calculated only by perturbation theory. The rotational constants for all the isotopomers were determined and the first transition dipole moments for NH⁺ ₃ and ND⁺ ₃ were plotted. A critical comparison of the perturbation and variational techniques suggests a possible further modification to the MULTIMODE algorithm for large systems.     

The effects of internal rotation on some infrared and electronic band contours of tetrolaldehyde

Contour calculations are reported for one electronic band and three infrared bands of tetrolaldehyde, CH₃CCCHO, where the methyl group executes relatively free internal rotation with respect to the body of the molecule. The electronic band described, the 0-0 band of the π^∗ ← n transition near 3760 Å, has the transition moment located in the molecular frame. The infrared bands are the 3 degenerate perpendicular bands of the methyl group, having the transition moments localized in the rotating group. Gross differences in contour are observed in the two types of bands.     

Accurate wavenumbers of the AΣ → XΠ (0, 0) and (1, 0) bands of OH and OD

The important A²Σ → X²Π (0, 0) absorption band of OH has been remeasured from spectra obtained by flash photolysis of H₂O₂ vapor. Accurate wavenumber measurements using thorium standards show that the previous rotational line measurements are about 0.1 cm^-1 too large. Measurements are also given for the (1, 0) band of OH and the (0, 0) and (1, 0) bands of OD.     

A spectrum of rhenium oxide

The arc emission spectrum of the ReO molecule has been photographed in the region 590–860 nm and three bands of a single electronic transition have been rotationally analyzed. The separation of lines of the isotopic molecules ¹⁸⁵ReO and ¹⁸⁷ReO leads to the conclusion that the vibrational assignments for these bands are 1-0, 0-0, and 0–1. It is conceivable that an electronic isotope shift of ～0.08 cm^?1 exists. The following vibrational and rotational data (cm^?1) have been determined: ν₀(0-0) = 14 038.42, $\text{Δ}\text{G′(}\text{1}\text{2}\text{) = 867.85}$, $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 979.14}$; B′_e = 0.3889, α′_e = 0.0019, B″_e = 0.4257, α″_e = 0.0043. It is concluded that Λ′ ? Λ″ = +1 with Λ″ ≥ 2.     

Heteronuclear double resonance study of pentafluorobenzene

The electronic absorption spectrum of solid Würster's blue perchlorate in the low temperature phase was measured at various temperatures, special attention being paid to the first π* ← π transition band of the monomer at ～ 600 mμ. The isosbestic points were clearly found for the spectral curves measured at several different temperatures, showing the coexistence of two transition bands in this wavelength region. By analysing the temperature dependence of the absorption intensity and by comparing the result with E.S.R. data, these two bands were interpreted as the singlet-singlet and triplet-triplet absorption bands originating from the ground singlet state and the thermally accessible triplet state, respectively. A similar result was obtained for the 260 mμ band. The present results can be interpreted by the dimer model for the low temperature phase of Würster's blue perchlorate but are inconsistent with the disproportionation mechanism for the phase transition.

The singlet-singlet and triplet-triplet transition bands were separately obtained for each of the 600 mμ and 260 mμ bands from analysis of the temperature dependence; the singlet-triplet separation in the corresponding excited states is 310±80 cm^-1 and 530±200 cm^-1, respectively, with the triplet state at lower energy.     

Electronic assignment as 1 A′(ππ*)-1 A′ of the 2980 Å system of 2-aminopyridine by rotational band contour analysis

In 2-aminopyridine the electronic origin band of the 2980 å electronic system, the longest wavelength system which has been observed, is shown to be a type B-type A hybrid band containing 55 ± 10 per cent of type A character. It follows that the electronic transition is ¹ A′-¹ A′ which implies a π*-π and not a π*-n electron promotion.

The degree of type A character is interpreted as indicating a swing of the transition moment by 10 ± 10° from the b axis of pyridine (the in-plane axis perpendicular to C ₂). Since it is expected that the first π*-π transition in pyridine has its transition moment polarized along the b axis the amino-group does not seem to perturb the pyridine transition strongly in this respect.

The changes of rotational constants from the ground to the excited state in 2-aminopyridine are very similar to those in aniline and probably reflect similar changes in geometry, namely a substantial contraction of the C-NH₂ bond, an opening of the internal ring angle adjacent to the substituent and a benzene-like expansion of the ring.

The origin of the 0-0 band is at 33471·1 ± 0·1 cm^-1.     

Raman study of datolite CaBSiO4(OH) at simultaneously high pressure and high temperature

Using an in situ method of Raman spectroscopy and resistance‐heated diamond anvil cell, the system datolite CaBSiO₄(OH) – water has been investigated at simultaneously high pressure and temperature (up to Р ~5 GPa and Т ~250 °С). Two polymorphic transitions have been observed: (1) pressure‐induced phase transition or the feature in pressure dependence of Raman band wavenumbers at P = 2 GPа and constant T = 22 °С and (2) heating‐induced phase transition at T ~90 °С and P ~5 GPа. The number of Raman bands is retained at the first transition but changed at the second transition. The first transition is mainly distinguished by the changes in the slopes of pressure dependence of Raman peaks at 2 GPa. The second transition is characterized by several strong changes: the wavenumber jumps of major bands, the merging of strong doublets at 378 and 391 cm⁻¹ (values for ambient conditions), the splitting of the intermediate‐intensity band at 292 cm⁻¹, and the transformation of some low‐wavenumber bands at 160–190 cm⁻¹. No spectral and visual signs of overhydration and amorphization have been observed. No noticeable dissolution of datolite in the water medium occurred at 5 GPa and 250 °С after 3 h, which corresponds to typical conditions of the ‘cold’ zones of slab subduction. Copyright © 2014 John Wiley & Sons, Ltd.     

Rotational analysis of the A2Πi → X2Πr band system of the sulfur monoxide cation,SO+

Six bands in the 0-v″ progression and three bands in the 1-v″ progression of the A²Π_i → X²Π_r visible system of SO⁺ have been recorded photoelectrically and rotationally assigned. Molecular constants for v′ = 0 and 1 in the A state and for v″ = 4–9 in the X state have been obtained using direct fitting and merging techniques.     

Fourier transform spectral study of BΣ-XΣ system of AlO

The spectrum of B²Σ⁺-X²Σ⁺ system of AlO has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution of 0.05 cm⁻¹. Nineteen bands of the Δv = 1, 0, −1, and −2 sequences of this band system have been analyzed for the rotational structure. Out of which seven bands, viz. 3-2, 4-3, 2-3, 3-4, 4-5, 5-6 and 6-7 have been analyzed for the first time. The rotational lines of these 19 bands along with 20 earlier analyzed bands, a total of 7200 lines, have been fitted in a simultaneous least squares fit. The study has resulted in determining more precise vibrational and rotational constants of the two states. Because of the high resolution employed it became necessary to invoke H₀ and H₁ coefficients, and a fifth order term to explain the anomalous spin-doubling observed in the v″ = 5, 6 and 7 levels of the X²Σ⁺ state.     

Infrared laser velocity modulation spectrum of the ν3 fundamental band of HBCI+

The infrared spectrum of the ν₃ fundamental band of HBC1⁺ has been observed using the velocity modulation detection technique. The ion was produced in an ac glow discharge containing a mixture of H₂ and BC1₃. Thirty-two transitions of the fundamental band of the most naturally abundant isotopomer, H¹¹B³⁵C1⁺, between 1105 and 1170cm^?1 have been assigned. The ν₃ band origin and rotational constants have been determined to be ν₀ = 1121.5677(20)cm^?1, B ₀ = 0.63089(23)cm^?1 and B ₁ = 0.62699(21)cm^?1. A second series of lines have been attributed to the H¹¹B³⁷C1⁺ isotopomer, although it has not been possible to make an unambiguous J assignment of these lines.