Emission and excitation spectra of Bi2Ge3O9:Eu3+

The emission and excitation spectra of the Bi₂Ge₃O₉:Eu crystal are observed at 77 K and 297 K. The spectra contain groups of sharp lines which are attributed to the transitions within 4f⁶ (Eu³⁺) configuration. The numbers of Stark splitting of terminal levels of transitions from ⁵D₀ and ⁷F₀ multiplets indicate that Eu³⁺ substitutes for Bi³⁺ in Bi₂Ge₃O₉. Tentative assignment of Stark levels of ⁷F_0-4 multiplets is made to crystal quantum numbers of C₃ symmetry which represents the site symmetry of Bi³⁺ in Bi₂Ge₃O₉. The following set of values of crystal field parameters of the C₃ point group is found to give the best overall agreement between the observed energy levels and the calculated levels: B²₀ = -533.84 cm^-1, B⁴₀ = 1085.99 cm^-1, Re(B⁴₃) = 327.57 cm^-1, Im(B⁴₃) = 75.209 cm^-1, B⁶₀ = 185.02 cm^-1, Re(B⁶₃) = - 68.475 cm^-1, Im(B⁶₃) = - 300.45 cm^-1, Re(B⁶₆) = 137.24 cm^-1 and Im(B⁶₆) = 882.29 cm^-1.     

12C18O2: High-resolution emission spectra in the 4.5-μm region rovibrational transitions 0v′2v3 → 0v′2(v3 − 1), v2 = l

Emission spectra of gaseous mixtures involving isotopic species of CO₂ excited by a dc discharge were recorded under Doppler-limited resolution, using a high-information Fourier Transform Interferometer, in the region 4–5 μm. In this paper are given the results concerning 34 vibrational transitions (Δv₃ = 1), for ¹²C¹⁸O₂. The band centers and the spectroscopic constants for the 39 vibrational levels involved are reported. They reproduce more than 1000 experimental wavenumbers with a RMS of the order of 2 × 10^?5 cm^?1 for the best vibrational transition and less than 3 × 10^?4 cm^?1 for most of the others. From a weighted simultaneous fit of all the experimental wavenumbers belonging to the Σ-Σ transitions, a set of molecular parameters was computed. A good reproduction of the experimental wavenumbers was obtained for all the vibrational transitions except those involving the level v₃ = 9, our conclusion being that a local vibrational perturbation exists for this level.     

12C16O18O: Analysis of rovibrational transitions Ov′2v3 → Ov′2(v3 − 1) (v2 = 0 and 1) observed in high-resolution emission spectra in the 4.5-μm region

Emission spectra of six isotopic species of CO₂ excited by dc discharge were recorded under Doppler limited resolution using the Fourier transform spectrometer of the Laboratoire d'Infrarouge in the 4.5-μm region. In this paper, the results concerning ¹²C¹⁶O¹⁸O are given. The band centers and the spectroscopic constants for 19 levels involved in vibrational transitions Δv₃ = 1 are reported. They reproduce 853 experimental wavenumbers with a RMS of the order of 2 × 10^?5 cm^?1 for the best vibrational transition, less than 1 × 10^?4 cm^?1 for most of the others. From experimental wavenumbers, to determine molecular parameters, it is shown that it is impossible to include in the same fit all the transitions Σ-Σ until v₃ = 10 using a polynomial representation of the rovibrational energy, the responsible phenomenon being the small Fermi resonance which occurs on Σ levels. Nevertheless, the 321 wavenumbers belonging to the first four vibrational transitions are satisfactorily reproduced by the model.     

High-resolution infrared and microwave spectroscopy of the ν4 and 2ν2 bands of 14NH3 and 15NH3

More than two thousand Stark resonances of the ν₄ and 2ν₂ band transitions of ¹⁴NH₃ and ¹⁵NH₃ were observed at Doppler-limited resolution with a CO laser. Fourier transform infrared spectroscopy on ¹⁵NH₃ is also carried out. Thirty-six new microwave transitions including seven perturbation-enhanced transitions are observed in the v₄ = 1 excited vibrational state of ¹⁴NH₃ and ¹⁵NH₃. Accuracies of all available spectroscopic data on the v₄ = 1 and the v₂ = 2 states are evaluated and analyses of the vibration-rotation spectra are performed. The Coriolis interaction between the closely lying v₄ = 1 a (antisymmetric level) and v₂ = 2 s (symmetric level) states is explicitly included in the analysis. Smaller Coriolis interactions between the v₄ = 1 a and the v₂ = 1 s states and between the v₂ = 2 s and the v₂ = v₄ = 1 a states (i.e., (v₁, v₂, v′₃, v′₄) = (0 1 0⁰ 1¹)) are also taken into consideration. The accuracy in determination of the principal molecular constants is 10^?6. The parameters thus obtained reproduce the frequencies of the vibration-rotation transitions and inversion transitions within the accuracy of 0.0024 cm^?1.     

A new emission of ZnS:Ni2+ arising from the 3T1(P) → 3T1(F) transition

A photoluminescence band with zero-phonon transitions at $\text{?}\text{= 12438 cm}{}^{-1}$ (this one subject to self-absorption) and at 12259 cm^-1 has been detected with ZnS:Ni crystals. Based on the appearance of these two lines, on the similarity of the whole spectrum with the ³T₂(F) → ³T₁(F) Ni²⁺ luminescence, and on preparation evidence, this new emission is interpreted as the ³T₁(P) → ³T₁(F) transition of substitutional Ni²⁺(3d⁸) ions in a tetrahedral crystal field.     

The ν2 and ν4 bands of AsH3

The infrared absorption of arsine, AsH₃, between 750 and 1200 cm^?1 has been recorded at a resolution of 0.006 cm^?1. Altogether 2419 transitions, including nearly 700 “perturbation allowed” transitions with Δ∥k ? l∥ = ±3, ±6, and ±9, have been assigned to the ν₂(A₁) and ν₄(E) bands. Splitting of the transitions for K″ = 3, 6, and 9 was also observed. To fit the rotational pattern of the v₂ = 1 and v₄ = 1 vibrational states up to J = 21, all the experimental data were analyzed simultaneously on the basis of a rovibrational Hamiltonian which took into account the Coriolis interaction between ν₂ and ν₄ and also included several essential resonances within them. The derived set of 38 significant spectroscopic parameters reproduced the 2328 transition wavenumbers retained in the final fit within the accuracy of the experimental measurements.     

Excitation spectra and fluorescent lifetime measurements of Mn2+ in CaF2 and CdF2

The excitation spectrum of the Mn²⁺ emission has been measured in CaF₂ and CdF₂. The observed excitation bands have been assigned to transitions of the Mn²⁺ ions in a cubic environment. The calculated values for the crystal field (Dq) and Racah parameters (B,C) are Dq = 425 cm^-1 for CaF₂, Dq = 500 cm^-1 for CdF₂ and, B = 770 cm^-1 and C / B = 4.48 for both compounds. The lifetime of the fluorescent level ⁴T_1g(⁴G) has been measured in both compounds at different temperatures in the range from 10 to 500 K. The lifetime thermal dependence is explained taking into account different mechanisms (purely radiative, phonon assisted, and radiationless transitions) for the decay of excited Mn²⁺ ions.     

Line Positions and Intensities of the ν1+ ν2+ 3ν3, ν2+ 4ν3, and 3ν1+ 2ν2Bands of Ozone

Using a Fourier transform spectrometer, we have recorded the spectra of ozone in the region of 4600 cm⁻¹, with a resolution of 0.008 cm⁻¹. The strongest absorption in this region is due to the ν₁+ ν₂+ 3ν₃band which is in Coriolis interaction with the ν₂+ 4ν₃band. We have been able to assign more than 1700 transitions for these two bands. To correctly reproduce the calculation of energy levels, it has been necessary to introduce the (320) state which strongly perturbs the (113) and (014) states through Coriolis- and Fermi-type resonances. Seventy transitions of the 3ν₁+ 2ν₂band have also been observed. The final fit on 926 energy levels withJ_max= 50 andK_max= 16 gives rms = 3.1 × 10⁻³cm⁻¹and provides a satisfactory agreement of calculated and observed upper levels for most of the transitions. The following values for band centers are derived: ν₀(ν₁+ ν₂+ 3ν₃) = 4658.950 cm⁻¹, ν₀(3ν₁+ 2ν₂) = 4643.821 cm⁻¹, and ν₀(ν₂+ 4ν₃) = 4632.888 cm⁻¹. Line intensities have been measured and fitted, leading to the determination of transition moment parameters for the two bands ν₁+ ν₂+ 3ν₃and ν₂+ 4ν₃. Using these parameters we have obtained the following estimations for the integrated band intensities,S_V(ν₁+ ν₂+ 3ν₃) = 8.84 × 10⁻²²,S_V(ν₂+ 4ν₃) = 1.70 × 10⁻²², andS_V(3ν₁+ 2ν₂) = 0.49 × 10⁻²²cm⁻¹/molecule cm⁻²at 296 K, which correspond to a cutoff of 10⁻²⁶cm⁻¹/molecule cm⁻².     

Analysis of the ν2 + ν3 band of 12CH4 and 13CH4

The ν₂ + ν₃ bands of ¹²CH₄ and ¹³CH₄ occurring in the region 4400–4650 cm^?1 have been studied from spectra recorded with a high-resolution Fourier transform spectrometer (resolution better than 0.01 cm^?1). Champion's Hamiltonian expansion, Canad. J. Phys.55, 1802 (1977), is applied to the problem of the two interacting F₁ and F₂ vibrational sublevels of this type of a band. As the P branch of ν₂ + ν₃ is strongly overlapped by neighboring bands, a combination-difference method, adapted to tetrahedral XY₄ molecules has been developed to help assignments of lines. A fit of 700 transitions has been performed using 13 new effective constants in the case of ¹²CH₄. In the case of ¹³CH₄, 532 transitions have been fit to 18 constants. The known parameters, relative to the vibrational ground state and the ν₃ state for both methanes, and the ν₂ state for ¹²CH₄ were fixed throughout. Most of the perturbed levels, up to J′ = 12, are well reproduced and the general agreement between experimental and calculated transitions is satisfactory with standard deviations of 0.047 cm^?1 (¹²CH₄) and 0.041 cm^?1 (¹³CH₄). The results (order of magnitude of obtained (ν₂ + ν₃) parameters and comparison of observed and computed intensities) indicate that the ν₂ + ν₃ band is perturbed by many other bands.     

Phonon density of states of CdI2 deduced fro,the fine structure of the 3A2g → 1Eg electronic transition of CdI2:Ni2+

The absorption and MCD spectra of the ³A_2g → ¹E_g transition of CdI₂:Ni²⁺ at about 12,500 cm^?1 have been measured. The unusual vibronic fine structure is explained by the coupling of the phonons of the CdI₂ lattice to the electronic states of Ni²⁺. The dispersion curves for the acoustical and optical branches in the Brillouin Zone of CdI₂ are deduced.     

Analysis of the ν3, A-type band of C2H3D

The ν₃, A-type band of C₂H₃D centered at 1288.780 cm^?1 has been analyzed up to J = 33 and K_a = 15. The spectral range from 1351 to 1235 cm^?1 was recorded with a grill-spectrometer “type Girard” and with a resolution of 0.06 cm^?1, and a wavenumber precision of about 2 × 10^?3 cm^?1. From 787 identified transitions it was possible to calculate the rotational energies in the ν₃ excited state, and to refine the corresponding set of parameters.     

The pentad rotation-vibrational states of 12CD4: Wavenumber analysis of infrared and Raman spectra of the ν1, ν3, 2ν2, ν2 + ν4, and 2ν4 bands

The so-called pentad of ¹²CD₄ consists of the vibrational states v₁ = 1(symmetry A₁), v₃ = 1(F₂), v₂ = 2(A₁ + E), v₂ = v₄ = 1(F₁ + F₂), and v₄ = 2(A₁ + E + F₂). All states are located in the 1950 to 2250-cm^?1 region and all are strongly interacting. In the present work we have assigned more than 5000 infrared rotation-vibrational transitions and 163 isotropic Raman transitions from the vibrational ground state to the pentad. We have used infrared and Raman spectra of a resolution better than 0.01 cm^?1. From the experimental wavenumbers 2567 pentad rotation-vibrational energy levels with J ≦ 20 have been determined. These levels are reported in the paper. The levels have been used for refinements of the spectroscopic constants of two physically different effective Hamiltonians for the pentad states. For all levels with J ≦ 12 an unweighted standard deviation of 0.004 cm^?1 is obtained for both Hamiltonians, whereas the standard deviation increases more or less rapidly with J above 12 due to the imperfections of the Hamiltonians. The values of the spectroscopic constants of both Hamiltonians (85 and 106, respectively) are reported and the effects of the approximations are discussed.     

A simultaneous analysis of the microwave,submillimeterwave, far infrared,and infrared-microwave two-photon transitions between the ground and ν2 inversion-rotation levels of 14NH3

Fourier transform infrared spectra of the inversion-rotation transitions have been measured with 0.010-cm^?1 resolution between 40 and 300 cm^?1 in the ground state and ν₂ excited states of ¹⁴NH₃. Submillimeterwave spectra of the inversion and inversion-rotation transitions in the ν₂ state of ¹⁴NH₃, including a few Δk = ±3 “perturbation-allowed” transitions, have been measured with microwave accuracy between 540 and 770 GHz. A simultaneous least-squares analysis of these data, the microwave ground-state transition frequencies, and the ν₂ infrared-microwave two-photon transition frequencies has been carried out. A theory of the Δk = ±3n interactions in the ground and ν₂ excited states of ammonia (S. P. Belov, L. I. Gershtein, A. F. Krupnov, A. V. Maslovskij, ?. Urban, V. ?pirko, and D. Papou?ek, J. Mol. Spectrosc.84, 288–304 (1980)) has been used in the analysis. A set of the ground- and ν₂-state molecular parameters has been obtained which describes the experimental data within the precision of the experiment. The “smoothed” values of transition frequencies can be used for calibration purposes with a precision better than 3 × 10^?5 cm^?1 in the submillimeterwave region, better than 10^?3 cm^?1 in the far-infrared region, and better than 1.5 × 10^?3 cm^?1 in the region 700 – 1200 cm^?1.     

Fluorescence spectra of matrix-isolated Se2

Laser induced fluorescence spectra are reported for samples of natural selenium and of the separated ⁷⁸Se and ⁸⁰Se isotopes in Ar and Kr matrices. The B(0_u⁺) → X(0_g⁺) and B(1_u) → X(1_g) systems of Se₂, already known in the gas, are observed by both single photon and biphotonic excitation considerably red-shifted in the matrices. The A(0_u⁺) → X(0_g⁺) emission of Se₂, not observed in the vapor, appears in the matrices with its origin near 15 100 cm^?1. Another system with ν₀₀ = 24 429 cm^?1 and ω″_e = 538 cm^?1 is thought to belong most probably to some polyatomic Se_n molecule.     

Fourier transform spectroscopy on the 3ν2, 2ν2 + ν6 and ν3 + ν5 bands of H2CO

Fourier transform spectra covering the range from 1500 to 5400 cm^?1 with 0.02-cm^?1 resolution have been obtained for formaldehyde. A study of the region above 4000 cm^?1 has yielded rotational constants and other asymmetric rotor parameters for three bands: 3ν₂ (ν₀ = 5177.7611 ± 0.0005 cm^?1)2ν₂ + ν₆ (ν₀ = 4734.193 ± 0.004 cm^?1), and ν₃ + ν₅ (ν₀ = 4335.102 ± 0.001 cm^?1). An analysis of the A-type Coriolis interaction between the 2ν₂ + ν₆ state and the unobserved 2ν₂ + ν₄ state has yielded partially deperturbed rotational constants for the 2ν₂ + ν₆ state. Vibration-rotation interaction constants have been obtained for the ν₂ and ν₆ normal modes by combining the present results with those of previous workers.     

High-resolution FTIR spectroscopy of the 3ν2 band of PH3

High-resolution Fourier transform spectrum of phosphine (PH₃) at room temperature has been recorded in the region of the 3ν₂ band (2730-3100 cm⁻¹) at an apodized resolution of 0.005 cm⁻¹. About 200 vibration-rotation transitions have been least squares fitted with an rms of 0.00039 cm⁻¹ after taking into account the ΔK = ±3 interaction.     

Analysis of the ν6 band of 12CH3D at 8.6 μm

The ν₆(E) fundamental vibration-rotation band of monodeuteromethane (¹²CH₃D) has been recorded in the spectral range 1033–1270 cm^?1 with a resolution of approximately 0.04 cm^?1. Of the 669 transitions with J′ ≤ 17 identified, 633 have been retained for the determination of the rotational levels in the upper state v₆ = 1. The Coriolis interaction between the v₆ = 1(E) and v₃ = 1 (A₁) vibrational states of ¹²CH₃D results in large A₁A₂ splittings of levels with v₆ = 1 and |K ? l₆| = 0 or 3; the mixing in K and l₆ also gives rise to some ten forbidden transitions observed in the spectra. These effects have been very well explained within the formulation based on the contact transformation method. Values of 15 molecular structure constants of the v₆ = 1 state have been determined from a least-squares analysis of the 633 retained transitions. These constants can be used to estimate values of the upper-state energies up to fourth order, and through them the spectral positions of the 633 retained transitions are reproduced with an overall standard deviation of 0.013 cm^?1, which is within experimental uncertainties.     

Infrared electronic transitions of Eu+3 in GdAlO3

Infrared ⁷F_O → ⁷F_J electronic transitions are reported for Eu⁺³ in GdAlO₃. The low symmetry of the crystalline field allows the observation, for the first time, of transitions with J = 3, 4, 5 and 6. The spectra are explained by means of a crystal-field model where a C_s term is added as a perturbation to the cubic field in order to take into account the lattice distortion. This model predicts energy levels which are in good agreement with the experimental data.     

External cavity tunable diode laser spectra of the ν1 + 2ν4 stretch-bend combination bands of NH3 and NH3

The ammonia ν₁ + 2ν₄ perpendicular stretch-bend combination band has been investigated in spectra of ¹⁴NH₃ and ¹⁵NH₃ recorded in the 6400-6800 cm⁻¹ region with an external cavity tunable diode laser (ECTDL) spectrometer. For ¹⁴NH₃, new assignments were determined initially by extrapolating from published low-J jet-cooled beam results up to transitions of higher J and K. Corresponding ν₁ + 2ν₄ transitions for the ¹⁵NH₃ species were then found by identifying similar patterns of lines with a characteristic downshift of approximately 9.7 cm⁻¹. Assignments were confirmed employing ground-state combination differences. Term values, a-s inversion splittings, l-doubling energies and parameter estimates from simple single-state fits are reported for the two ammonia species.     

Observation of electronic Raman transitions from the transition metal ions Ti3+ and V4+ highly diluted in α-Al2O3

α-Al₂O₃ : Ti³⁺ (300 mass ppm concentration) at 10 K shows two electronic Raman transitions at 38 cm^-1 and 109 cm^-1. The E symmetry of the scattering matrix agrees with the selection rules for transitions between the ground state B_{$\text{3}\text{2}$} and the E_{$\text{1}\text{2}$} of the ground state manifold ²t_2g.α-Al₂o₃ : V⁴⁺ shows two very weak electronic Raman transitions at about 30 cm^-1 and 56 cm^-1 respectively.