nπ1 Transitions in tetramethyl-1,3-cyclobutanedithione-h12 and -d12

The polarized low-temperature crystal absorption spectra of tetramethyl-1,3-cyclobutanedithione-h₁₂ and -d₁₂ have been measured in the visible region, and $\text{nπ}{}^1$ excited states identified as follows: ³A_u with origin ($\text{h}{}_{12}\text{d}{}_{12}$) at $\text{16 829}\text{16 836}\text{cm}{}^{\mathrm{?1}}$; ¹A_u and ¹B₁₀ with nearly degenerate origins near 18 000 cm^?1; and probably ¹A_u and ¹B_1g near 19 500 cm^?1. The singlet excited states lie close together and perturb each other strongly. As in the corresponding dione, $\text{CH}\text{CD}$ stretching vibrations of the substituent methyl groups are active in intensity borrowing, and the effects of excitation are delocalized over the entire molecule.     

Interpretation of electronic spectra by configuration analysis: Absorption spectra of monosubstituted naphthalenes

The electronic absorption spectra of four monosubstituted naphthalenes, α-, β-naphthols, and α-, β-naphthylamines have been investigated by means of configuration analysis with particular attention to the dependence of spectra on the position of substitution and on the electron-donating power of the substituent. The results of molecular orbital calculations based on the Pariser-Parr-Pople method are analyzed in terms of locally excited states and intramolecular charge-transfer configurations. The characteristic changes in location and polarization of the L_b, L_a, and B_b bands caused by substitution at the α- or β-position are adequately explained by the analysis. Two strong absorption bands of α-substituted naphthalenes, which appear in place of the B_b band of naphthalene, are shown to result from a mixing of the $\text{B}{}_{\mathrm{3u}}{}^{\mathrm{+}}\text{(B}{}_{\mathrm{b}}\text{)}$ and $\text{A}{}_{\mathrm{g}}{}^{\mathrm{?}}$ states. The amino group exerts a great influence on the electronic structure of the parent molecule, so that the B_b band cannot be identified in the spectrum of β-naphthylamine.     

Inelastic scattering and satellite fine structure in the high-resolution uv photoelectron spectrum of CS2

The outer valence region in CS₂ has been studied by high-resolution UV photpelectron Spectroscopy. The spectra reveal detailed vibrational structure in the X$\text{\$}\text{?}$²Π_g, A$\text{\$}\text{?}$²Π_u, B$\text{\$}\text{?}$²Σ⁺_u and C$\text{\$}\text{?}$²Σ⁺_g bands. Some of the fine-structure peaks in the X$\text{,}\text{?}$B$\text{\$}\text{?}$and C$\text{\$}\text{?}$bands are shown to be pressure-dependent. The reason for the pressure dependence is assumed to be inelastic scattering of electrons emitted in the adiabatic transitions. It is established that the two CI satellite bands present in the He(I)-excited spectrum contain vibrational structure.     

Rotational analysis and radiative lifetime measurement on the 2B1 (K′ = 0) excited state of NO2 with v′2 = 6, 7, 8, and 9

The rotational structure of the ²B₁ (K′ = 0) subbands of NO₂ with v′₂ = 6, 7, 8, and 9 were analyzed by means of the time-gated excitation spectrum. The excitation spectrum monitored at ν₂, 2ν₂, or 3ν₂ fluorescence band was fairly simplified in comparison to its corresponding absorption spectrum. The band origins and rotational constants are evaluated from the observed data: ν₀ = 20205.0 cm^?1, $\text{B}\text{′ = 0.374}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 6; ν₀ = 21104.4 cm^?1, $\text{B}\text{′ = 0.374}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 7; ν₀ = 22001.9 cm^?1, $\text{B}\text{′ = 0.375}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 8ν₀ = 22898.0 cm^?1, $\text{B}\text{′ = 0.375}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 9. The value of $\text{B}\text{′}$ extrapolated to v′ = 0 is 0.370 cm^?1. This value corresponds to the bond length of 1.19 Å. Fluorescence decays of these excited levels were also studied. Radiative lifetimes obtained by extrapolation to zero pressure from the $\text{1}\text{τ}\text{– P}$ plots were 25–40 μsec. The short-lived excited levels previously reported by some authors were not found.     

Laser-excited phosphorescence spectrum of C3S2 in an Ar matrix

The phosphorescence spectrum of C₃S₂ was observed in a low-temperature Ar matrix with excitation of an Ar⁺ laser. The spectrum consists of a very strong 0-0 band at 18 287 cm^?1 and well-resolved progressions in the ν₂, ν₅, ν₆, and ν₇ vibrations. Side bands were found on the high-energy sides of some transitions. The separation between the main and side bands is 23 cm^?1. Polarization analysis suggests that C₃S₂ is linear symmetric in the Phosphorescent state as in the ground electronic state. On the basis of symmetry considerations and a qualitative evaluation of spin-orbit coupling, the phosphorescent state is assigned to ³Σ_u^? with Σ_u⁺ and Π_u components split by spin-spin interaction. The Σ_u⁺ level is lower than the Π_u one by 23 cm^?1 and the main and side band emissions start from the Σ_u⁺ and Π_u levels, respectively. The Σ_u⁺ component seems to acquire allowed character from a ¹Σ_u⁺ state by spin-orbit coupling and from bent ${}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}\text{(}{}^1\text{B}{}_2\text{)}$ and ${}^1\text{Δ}{}_{\mathrm{g}}\text{(}{}^1\text{A}{}_1\text{+}{}^1\text{B}{}_2\text{)}$ states by ν₅ vibronic coupling. Mixing of the Σ_u⁺ and Π_u components through ν₅ is responsible for most of the side bands. The ν₅ frequency is estimated to be 160 ± 20 cm^?1 in the ³Σ_u^? state from the intensities of ν₅ progression bands and from the ground-state frequency, 411 cm^?1.     

A study of the excited electronic states of 9-fluorenone

Some spectroscopic properties of the low-energy electronic states of 9-fluorenone have been examined. The spectra in paraffin matrices at 4.2°K show detailed vibrational spectra. Two fluorescence spectra are observed; a diffuse emission arises from 9-fluorenone crystals in the paraffin matrix, and a sharp emission is characteristic of the molecule. The sharp fluorescence is analyzed in terms of known a₁ vibrational fundamentals. The sharp absorption is a near mirror-image to the fluorescence, so Herzberg-Teller vibrations are not prominent. The polarization in the crystal spectrum allows this low-energy transition near 23 000 cm^?1 to be assigned ${}^1\text{B}{}_2\text{←}{}^1\text{A}{}_1$. Because there is no vibronic perturbation in fluorescence, and certainly no out-of-plane modes, a $\text{π}{}^1\text{← n}$ transition seen at about 26 000 cm^?1 is tentatively assigned ${}^1\text{B}{}_1\text{←}{}^1\text{A}{}_1$. Another sharp absorption system is seen at 31 000 cm^?1 in the paraffin matrices at 4.2°K (linewidth 6 cm^?1) but no fluorescence was detected. The polarized crystal spectrum indicated the assignment of this system and another very strong system at 40 000 cm^?1 to be ${}^1\text{B}{}_2\text{←}{}^1\text{A}{}_1$, while other systems at about 34 000 cm^?1 and 44 000 cm^?1 are ${}^1\text{A}{}_1\text{←}{}^1\text{A}{}_1$.The phosphorescence spectrum of pyrene-d₁₀ held in a single crystal of 9-fluorenone at 4.2°K has been recorded. No delayed fluorescence from the host crystal is observed at 4.2°K but is intense at 77°K. The energy difference between host and guest triplet levels is estimated to be about 900 cm^?1 allowing the lowest triplet state of 9-fluorenone to be placed at 17 800 cm^?1.     

Optical absorption spectrum of hematite, αFe2O3 near IR to UV

Optical absorption spectra have been measured on thin (011) single crystal platelets and on highly oriented (110) thin films of αFe₂O₃. We have observed and assigned some of the absorption bands predicted by ligand field theory and SCF-Xα calculations. The temperature dependence of the 11760 cm^?1 single crystal band has been fitted to the function $\text{? = ?}{}_0\text{(1 + exp (?}\text{θ}\text{T}\text{))}$ with $\text{?}{}_0\text{= 0.85 × 10}{}^{\mathrm{?4}}$ and θ = 200 K (139 cm^?1). We have measured the photocurrent as a function of wavelength and have found several peaks that coincide with optical absorption bands.     

Electronic spectrum of 1,5-naphthyridine: Crystal spectra

Polarized spectra (4 K) of the following systems are recorded in the region 26 000 – 29 000 cm^?1 ($\text{π}{}^1\text{← n}$ transition): 1,5-naphthyridine-d₀ in durene, p-xylene, neat crystal and naphthalene; 1,5-naphthyridine-d₆ in durene and in naphthalene. The spectra in naphthalene differ radically from the others, which resemble the vapor spectrum in being built principally upon two main origins interpreted as the true origin 0 and a vibronic origin (6a_u)₀¹ near 0 + 183 cm^?1 (0 + 163 cm^?1, -d₆). The favored interpretation of the naphthalene spectrum, which is polarized in the molecular plane, invokes an origin (L-polarized), but (6a_u)₀¹ is missing, and there are then three further vibronic origins, each with distinctive polarization at 0 + 309, 0 + 362, 0 + 516 cm^?1 (-d₀), 0 + 312, 0 + 384, 0 + 492 cm^?1 (-d₆). The changed appearance of the spectrum in naphthalene is attributed to a diminution, because of an increased spacing between the interacting states, of the strong vibronic coupling which is considered to exist between the n, $\text{π}{}^1$ state and two higher π, $\text{π}{}^1$ states.     

Probable location of a 1E2g state of the benzene molecule

Photoexcitation spectra of benzene in rare gas matrices show a previously unreported transition near 46000 cm^?1. The observed bands are not explicable in terms of site splittings, impurity states, aggregation effects, intermediate radius states of the matrix, triplet states, excimer states, exciplex states or $\text{σ-π}{}^1$ transitions. The vibronic spacings in these spectra could be those expected for a ¹E_2g ← ¹A_1g transition and on this and other evidence we argue that the ordering of origins of the first four spin allowed intravalence states of benzene is ¹B_2u (38086 cm^?1), ¹E_2g (near 46400 cm^?1), ¹B_1u (48450 cm^?1) and ¹E_1u (55430 cm^?1). Our data also show that the transition ¹B_1u ← ¹A_1g accounts for most of the intensity of the 210 nm absorption band system. Our ordering of the spin allowed states permits interpretation of experimental data of others, confirms certain semi-empirical and ab initio SCF MO CI calculations in which account is taken of higher excitations and illustrates the necessity of including such higher excitations. The intensity of the ¹E_2g ← ¹A_1g transition is at least an order of magnitude less than previously calculated indicative of the difficulty of choosing suitable wavefunctions for the ¹E_2g state and of calculating “forbidden” transition probabilities.     

Electronic spectrum of 1,5-naphthyridine: Vapor spectra

Analyses of the vapor spectra of 1,5-naphthyridine-d₀ and -d₆ are presented. The spectra are characterized by two principal origins, one the true electronic origin, magnetic dipole allowed, ${}^1\text{B}{}_{\mathrm{g}}\text{←}{}^1\text{A}{}_{\mathrm{g}}$, 27 598.5 cm^?1 (-d₆ 27 676.9), and the other a vibronic origin, electricd-dipole allowed, corresponding to the activity of a low-frequency vibration 6a_u, 183 cm^?1 (-d₆ 163). Extensive sequence structure is evident and the relative intensities of the sequence bands associated with the two origins provide the strongest argument for their assignments. The absence of 6a_u as a major source of intensity in the hot bands is in agreement with vibronic coupling calculations which propose that in absorption intensity “flows” to the lower-frequency vibrations.     

The infrared spectrum of OH-compensated defect sites in C-doped MgO and CaO single crystals

The IR spectra of OH-compensated point defects in MgO (and CaO) single crystals of various purity grades were reinvestigated. Three distinct groups of IR bands appear in the O-H stretching region: A, B and C around 3550 cm^?1 (3650 cm^?1), 3300 cm^?1 (3450 cm^?1) and 3700cm^?1 (3750cm^?1). They are assigned as follows: band A to the fully compensated, band B to the half compensated and band C to the overcompensated cation vacancies, [O?V”_catH?]^×, [O?V”_cat], and [O?O?V”_catH?$\text{]}\text{?}$, respectively.Upon cooling to 80 K the band A shows a complex behavior partly due to the formation of Ha molecules by charge transfer and concommittant O^? formation: [? (H₂)”_cat?]^×. The O^? represent defect electrons or positive holes in the O^2? matrix.Bands A and B show a characteristic multiplet splitting which is caused by local lattice strains coming from carbon atoms on near-by interstitial position. The intensity ratios between the multiplet components remain constant regardless of temperature pretreatments up to 1470 K, but strong variations of the integral intensities are observed. These are caused by the highly mobile C atoms entering and leaving reversibly the cation vacancy sites as a function of temperature and of the quenching speed. When the C atoms push the H₂ molecules onto interstitial sites, an H-H stretching signal appears around 4150cm^?1.     

The 370-nm electronic spectrum of tropolone: Evidence from single vibronic level fluorescence spectra regarding the assignment of some vibrational fundamentals in the X̃ and à states

Single vibronic level fluorescence (SVLF) spectra of tropolone from vibronic levels in the $\text{A}\text{?}{}^1\text{B}{}_2$ electronic state, in combination with recently reported supersonic jet spectra, have enabled the assigning of many absorption bands in the region of 0₀⁰ which had previously been impossible. Some of the complexity in these bands has been shown to be due to a large Duschinsky effect involving the two lowest b₁ vibrations, ν₂₅ and ν₂₆. It has been shown that these vibrations have wavenumbers of 176 and 110 cm^?1, respectively, in the $\text{X}\text{?}$ state, and 172 and 39 cm^?1 in the $\text{A}\text{?}$ state. This last value shows how unresistent the molecule is in the $\text{A}\text{?}$ state to out-of-plane bending in the region of the five-membered ring. Other aspects of the vibrational complexity are due to the effect of ν′₂₆ in increasing the barrier to tunnelling of the hydrogen-bonding proton in the $\text{A}\text{?}$ state contrasting with very little effect of ν″₂₆ in the $\text{X}\text{?}$ state.     

Rotational analyses and vibrational assignments of the 463- and 474-nm bands of NO2

The excitation spectrum of NO₂ was investigated in the blue region by using a Nd:YAG laser-pumped dye laser. The 463- and 474-nm bands of the ²B₂-²A₁ system were identified and analyzed using the simplification that occurs if the excitation spectrum is monitored at particular wavelengths. Band origins and rotational constants were obtained. Vibrational assignments have been given to these bands by comparing the Franck-Condon Factors calculated for the ²B₂-²A₁ system with the fluorescence intensities of bands going to different vibrational levels of the ground state. The vibrational assignments and molecular constants obtained in this work are (v′₁, v′₂, v′₃) = (3, 11, 0)ν₀(K′ = 0) = 21584.1, $\text{B}\text{= 0.405}$, and $\text{∥}\text{?}\text{′∥ = 0.05}\text{cm}{}^{\mathrm{?1}}$ for the 463-nm band; and (v′₁, v′₂, v′₃) = (2, 12, 0), ν₀(K′ = 1) = 21104.9, $\text{B}\text{= 0.408}$, and $\text{∥}\text{?}\text{′∥ = 0.03}\text{cm}{}^{\mathrm{?1}}$ for the 474-nm band.     

Rotational analysis of the 8000–9000 Å bands of nitrogen dioxide

The rotational structure of bands of NO₂ vapor in the region 8300–9000 Å has been partially analyzed and the absorption assigned to the (000)-(000) and (000)-(010) vibronic bands of the $\text{A}\text{?}{}^2\text{B}{}_2\text{←}\text{X}\text{?}{}^2\text{A}{}_1$ electronic transition. Irregular weak perturbations in the N-structure of the upper-state manifold are accompanied by larger resonance-type crossings in the K-structure. The larger perturbation is attributed to vibronic coupling between the à state and excited vibrational levels of the ground state, characterized by a low density of ground state levels and a large vibronic coupling matrix element between the à and X? states. The reconstituted, deperturbed bands have blue-degraded N-structure and strongly red-degraded K-structure, indicating that the bond angle decreases sharply in the excited state. The physical structure of the ²B₂ state is uncertain but some suggestions are made. The electronic energy of the ²B₂ state is T₀ = 11 962.9 cm^?1.     

The visible and photographic infrared spectrum of osmium oxide

The emission spectrum of OsO has been photographed in the region 405–875 nm where many new bands have been observed. In favorable cases the ${}^{190}\text{OsO}{}^{192}\text{OsO}$ isotopic splittings have been resolved and aid in vibrational assignments. Three visible bands in the region 433–470 nm have been assigned as (1,0), (0,0), and (0,1) of a $\text{ΔΩ}\text{= 0}$ electronic transition. The (0,0) and (0,1) bands have been rotationally analyzed, yielding principal constants (cm^?1) for the visible system of ν₀ = 22 273.3, B′₀ = 0.3657, D′₀ = 2.8 × 10^?7, B″_e = 0.4023, D″_e = 3.2 × 10^?7, $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 780.7}$, and $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 884.9}$. A band at 825.4 nm has been found to be a $\text{ΔΩ}\text{= +1}$ (0,0) band with the same lower state as in the analyzed visible bands. Constants for the upper state of the ir system are ν₀ = 12 109.7, B′₀ = 0.3845, and D′₀ = 3.1 × 10^?7 cm^?1.     

The B̃2Σ−g (Πu) ← X̃2A1 system of nitrogen dioxide in neon matrices

The $\text{B}\text{?}\text{←}\text{X}\text{?}$ band system of NO₂, ${}^2\text{Σ}{}^{\mathrm{?}}{}_{\mathrm{g}}\text{(π}{}_{\mathrm{u}}\text{) ←}{}^2\text{A}{}_1$, has been measured in absorption in a neon matrix at 6 K, using ¹⁵NO₂ and N¹⁸O₂ in addition to the normal isotope. The spectrum consists essentially of a single, long progression of bands terminating on successive levels of the bending mode in the upper state. Transitions to odd- and even-v₂′ states occur with a uniform intensity distribution indicating that the rotation of the bent ground state of NO₂ about its near-prolate axis is hindered in the matrix. The observations strongly suggest that the top axis of the molecule coincides with a C₂ axis of neon crystals in the polycrystalline matrix. Relative to the vapor absorption the matrix spectrum is red shifted by about 150 cm^?1, the crystal field parameter V₂ and principal constants of the $\text{B}\text{?}$ state of ¹⁴N¹⁶O₂ in neon being

$\text{T}{}_{010}\text{14 571 cm}{}^{\mathrm{?1}}\text{: x}{}_{22}\text{, ?0.3 cm}{}^{\mathrm{?1}}\text{;}$

$\text{w}{}_2\text{460.2 cm}{}^{\mathrm{?1}}\text{: V}{}_2\text{, 80 cm}{}^{\mathrm{?1}}\text{.}$

     

Temperature dependence of the lattice vibrations of triglycine selenate

The polarized Raman spectra below 300 cm^?1 and the far infrared spectra from 400 to 30 cm^?1 of triglycine selenate were measured at various low temperatures. It was found that the Raman doublet at 44 and 38 cm^-1 observed in the paraelectric phase (space group C²_2h) was reduced to a singlet at 38 cm^?1 in the ferroelectric phase (space group C₂²). This spectral anomaly in the paraelectric phase appears to be due to the splitting of the translational mode of glycine I along the crystallographic b axis, the splitting being caused by the tunneling of glycine I across the barrier between the two potential minima which are located symmetrically on either side of the crystallographic ac plane (i.e. at $\text{b =}\text{1}\text{4}$ and $\text{3}\text{4}\text{)}$. New Raman bands which appear below the Curie temperature are also discussed.     

The D′ → A′ transition in Br2

A vibrational and rotational analysis is presented for the D′ → A′ transition (2800–2950 Å) of Br₂. The analysis includes 11 rotationally analyzed bands for ⁷⁹Br₂ and 3 for ⁸¹Br₂, plus bandheads for 70 additional v′-v″ bands of ⁷⁹Br₂, ⁸¹Br₂, and ⁷⁹Br⁸¹Br. The latter include some violet-degraded and spikelike features at the long-wavelength end of the spectrum, which are interpreted and assigned with the aid of band profile simulations. The assigned features are fitted directly to 14 vibrational and rotational expansion parameters for the two electronic states, from which the following spectroscopic constants are obtained: ΔT_e = 35706 cm^?1, ω′_e = 150.86 cm^?1, ω″_e = 165.2 cm^?1, B′_e = 0.042515 cm^?1, B″_e = 0.05944 cm^?1, $\text{R′}{}_{\mathrm{e}}\text{= 3.170}\text{A}\text{?}$, $\text{R″}{}_{\mathrm{e}}\text{= 2.681}\text{A}\text{?}$. The spectroscopic parameters are used to calculate RKR potentials and Franck-Condon factors for the transition.     

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.     

The a-X electronic band system of selenium monoxide at 1.8 μm

The emission spectrum of the SeO molecule excited in a microwave discharge and recorded at low resolution revealed the existence of a brief band system in the near-infrared region 6470-5560 cm^?1. The system consists of five bands divided into two groups which were assigned as the Δv = 0 and +1 sequences of the transition a2-X₂1 (X being the case ?c³Σ^? ground state). An approximate value of the rotational constant B₀ of state a was obtained from the observed separation between the Q and R heads of the 0-0 band and the known value of B₀ of state X. The derived molecular parameters of state a are: ν₀₀ = 5566.2 cm^?1, $\text{Δ}\text{G(}\text{1}\text{2}\text{) = 833.3}\text{cm}{}^{\mathrm{?1}}$, B₀ = 0.45₆ cm^?1.