Optical phonons in CuAlS2

The optical phonons at k=0 of CuAlS₂ have been investigated by Raman scattering, infrared reflectivity and absorption measurements from 50 to 1000 cm^-1 at T=300 K. Eleven of the thirteen expected optically active phonons have been observed and identified with respect to their symmetry types. The phonon frequencies appear in a range from 498 to 76 cm^-1 with predominant polar modes at 445 and 266 cm^-1. The dielectric dispersion for E ⊥ c and E ∥ c has been determined by Kramers-Kronig integrations.     

Raman and infrared spectra of ZnSiAs2

The optical phonons at k = 0 of ZnSiAs₂ have been investigated by Raman scattering and infrared reflectivity measurements at 300 K. Eleven of thirteen expected optically active phonons have been observed and identified with respect to their symmetry types. The phonon frequencies appear in the range from 415 cm^-1 to 75 cm^-1 with predominant polar modes at 400 cm^-1 (gG₅), 389 cm^-1 (Γ₄) and 242 cm^-1 (Γ₄). The dielectric dispersion for E ⊥ c and E 6 c has been determined by Kramers-Kronig integrations.     

Anharmonicity in silicate crystals: Temperature dependence of Au type vibrational modes in ZrSiO4 and LiAlSi2O6

Infrared reflection spectra for the extraordinary ray of zircon and spondumene have been obtained in the frequency range from 270 to 1500 cm^?1 and from room temperature up to 1300°K. Using a combination of Kramers-Kronig analysis and a classical dispersion theory, the oscillator parameters of the A_2u modes in zircon and A_u modes in spodumene were determined. The temperature dependence of observed mode damping is analysed on the basis of quantum theoreticall results involving both cubic and quartic anharmonic contributions. The comparison of the present results with other data reported in previously studied silicate crystals, shows that the observed anharmonic behavior of internal and external modes is consistent with simple considerations based on the site vicinity of each ion.     

Measurement and analysis of the ν2 band of D216O

The rotational structure of the ν₂ band of D₂¹⁶O between 700 and 1550 cm^?1 has been analyzed from spectra recorded with a Fourier transform spectrometer (nominal resolution: 0.1 cm^?1). By applying Watson's reduced Hamiltonian and a least squares method to the set of observed transitions, together with microwave data and the infrared data of Williamson, 22 rotational constants for the ground state and 17 for the upper state have been obtained which predict the positions of more than 700 observed lines with a standard deviation of 0.04 cm^?1.     

Ring-puckering combination band spectra of 1,3-disilacyclobutane in the SiH2 stretching region

Three sets of sum bands and two sets of difference bands arising from the combination of the ring-puckering vibration with SiH₂ stretching modes have been observed between 2060 and 2260 cm^?1 in the infrared spectrum of 1,3-disilacyclobutane. An unusual feature of the spectrum is that there is little correlation in intensity between corresponding sum and difference bands. An additional sum band and a difference band were also observed in the Raman spectrum. The spectra confirm the low-frequency ring-puckering assignment and verify the position of the weak 2–3 transition near 31 cm^?1. The puckering levels in the excited states of the SiH₂ stretching modes are virtually unshifted relative to the ground state demonstrating that negligible coupling exists between these vibrations. In addition, sum and combination bands have been observed off an SiD₂ stretching mode for 1,3-disilacyclobutane-1,1,3,3-d₄.     

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.     

Far infrared optical properties of proustite (Ag3AsS3)

The infrared reflection and transmission spectra of Ag₃AsS₃ single crystals have been between 20 and 650 cm^-1 at room temperature. Fourteen phonon modes were observable in reflectivity with the dominant restrahlen bands occuring at 360 cm^-1 and 35 cm^-1 for E? c and at 335 cm^-1 and 35 cm^-1 for E⊥ c. These measurements indicate that generation of far infrared radiation by mixing of two laser frequencies using proustite as the down-conversion crystal is not possible.     

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.     

An inelastic neutron scattering study of C2H2 adsorbed on type 13X zeolites

The inelastic neutron scattering spectra of C₂H₂ and C₂D₂ adsorbed on a Ag⁺ exchanged 13X zeolite (0–800 cm^?1) and of C₂H₂ on the Na⁺ form (0–300 cm^?1) have been obtained. For the Na-13X system no distinct vibrational modes were observed, however for the Ag-13X systems the low frequency intramolecular modes of the adsorbed gas and some of the vibrations of the adsorbed gas relative to the surface have been assigned. From the deuteration shifts it appears that C₂H₂ and C₂D₂, adsorbed on Ag-13X, are non-linear.     

Vibrational spectra and force constants of symmetric tops: ν1, ν5, and 2ν5 of CF335Cl and CF337Cl

The gas phase infrared spectra of CF₃³⁵Cl and CF₃³⁷Cl have been recorded in the ν₁ region and 2ν₅ regions with a resolution of 0.09 cm^?1. Additionally the ν₅ fundamental of CF₃Cl, with natural isotopic abundance, has been reinvestigated with a resolution of approximately 0.36 cm^?1. Molecular constants have been evaluated from the observed spectra by means of polynomials and band contour simulation. The possibility of a Fermi resonance between ν₁ and 2ν₅ is discussed.     

Raman spectra of the orthorhombic semiconductor compound Cu2SnTe3

The optical phonon spectrum of the semiconductor Cu₂SnTe₃, that crystallizes in the orthorhombic structure with space group Imm2 (), have been studied by measuring unpolarized Raman scattering between 10 and 300 K. The experimental frequencies of the phonon modes observed were compared to those calculated by using simplified lattice dynamical models reported in the literature. From combined analysis of these results together with the factor group analysis of the zone-center vibrational modes, valuable information about these modes was obtained and their possible symmetry was assigned. A₁ modes at 71, 123, 167, 176 and 190 cm⁻¹; A₂ modes 115 and 131 cm⁻¹; B₁ modes at 76, 142 and 152 cm⁻¹; B₂ modes at 89, 100 and 206 cm⁻¹; a overtone at 246 cm⁻¹, and combinations at 218, 270 and 292 cm⁻¹; have been observed in this compound.     

Lattice vibrations of MgAl2O4 spinel

Raman spectra have been measured on oriented single crystals of MgAl₂O₄ spinel. The fundamental frequencies are A_1g = 772, E_g = 410, and T_2g = 671, 492 and 311 cm^?1. A Kramers-Kronig analysis of the reflectance spectrum of spinel yields the i. r. -active vibrations T_1u = 670, 485, 428 and 305 cm^?1.     

Absorption spectra of C6H6 and C6D6 near 340 nm

The absorption spectra of C₆H₆ and C₆D₆ in the liquid phase have been studied near 340 nm. The absorption spectrophotometric mounting was a sequential double-beam attachment with linear response to energy on scanning of the spectrum before the exit slit and an electronic device which gives directly either the absorbance or the integrated absorbance of a transition and, consequently, its oscillator strength.The oscillator strength measured for the band of C₆H₆ is 8×10^?8, which corresponds to a dipole moment of 2.4×10^?3 Debye; this value is of the same order as a theoretical value calculated by Tsubomura and Mulliken (3.8×10^?3 Debye) for a transition between states ³F and ³A of an oxygen-benzene pair. This agreement corroborates the hypothetical existence of such a transition.The first vibrational band is at 28553 cm^?1 for C₆H₆; this band is not observed in the vapor or solid phase. It corresponds probably to the transition 0-0, which is considered in the literature to be near 29500 cm^?1. The isotopic shift measured for this first band is 164 cm^?1. The vibrational frequencies are, respectively, 910 cm^?1 for C₆H₆ and 889 cm^?1 for C₆D₆.     

High resolution infrared spectrum of the ν2 + ν3 and ν1 + ν2 bands of ozone

The vibration-rotation bands ν₁ + ν₂ and ν₂ + ν₃ of ozone appearing in the 5.7 μm region have been recorded at a resolution of 0.019 cm^?1 with a SISAM spectrometer. The rotational levels of the (110) and (011) vibrational states have been fitted using a Hamiltonian which takes into account the Coriolis interaction between these two states. The rotational and coupling constants deduced from this study have been used to calculate a list of the vibration-rotation lines which is of interest for high resolution studies of atmospheric spectra in the 1670–1890 cm^?1 region.     

Emission and excitation spectra of CCl2 in solid argon

Studies of the CCl₂ excitation spectra in solid argon give values of 624 and 304 cm^?1 for the upper-state vibrational modes ν₁ and ν₂, respectively. The 000-000 band of the electronic transition occurs at 17 092 cm^?1. Vibrational relaxation in the upper state is fast compared with the 3.6 μsec emission lifetime, and only vibrationally relaxed emission is observed.     

Raman and infrared spectra of CdIn2S4 and ZnIn2S4

Four one-phonon Raman lines have been found in CdIn₂S₄ (ZnIn₂S₄) spinels at 92 (72) cm^-1, 186 (184) cm^-1, 246 (253) cm^-1, and 367 (372) cm^-1 for incident photon energies well below the energy gap E_G ～ 2.4 (2.2) eV at 300 K. For photon energies close to E_G, the 367 cm^-1 mode underwent a resonant enhancement in CdIn₂S₄ and four infrared active but Raman forbidden F_1u modes appeared in the CdIn₂S₄ and ZnIn₂S₄ Raman spectra: TO modes at 226 (221) cm^-1 and 309 (312) cm^-1, and LO modes at 274 (272) cm^-1 and 340 (342) cm^-1.     

Analysis of the ν2 and ν4 infrared bands of CD4

The infrared spectrum of totally deuterated methane CD₄ has been recorded between 930 cm^?1 and 1180 cm^?1 under high resolution (0.003 cm^?1). The ν₂ and ν₄ bands of ¹²CD₄ have been reanalyzed on the basis of a complete third-order Hamiltonian including all the coupling terms linking the upper states of the two bands. A set of only 16 self-consistent parameters have been adjusted to fit more than 1650 assigned transitions reaching a maximum upper state J value of 20. The obtained standard deviation is 0.0041 cm^?1. In addition, 171 lines of the ν₄ band of ¹³CD₄ have been assigned. They have been analyzed, in the same dyad scheme, by adjusting 7 parameters of the ν₄ band together with the main ζ₂₄ Coriolis parameter. The obtained standard deviation is only 0.0012 cm^?1.     

High-resolution infrared atmospheric spectra of ozone in the 10-μm region: Analysis of ν1 and ν3 bands-assignment of the (ν1 + ν2) − ν2 band

1988 lines of ozone have been observed in the atmospheric spectrum in the region 1060 to 1220 cm^?1, 1394 of them have been assigned to the ν₁ band, and 480 to the ν₃, particularly corresponding to ΔK_?1 = 2. The analysis has been performed using the Watson Hamiltonian, taking account of the strong Coriolis coupling between the 001 and 100 levels. The constants for the latter two states, the spectra and a listing of the observed and calculated wave-numbers, with their assignment, are given. In addition, 114 lines of the “hot” band (ν₁ + ν₂) ? ν₂ have been observed and assigned and are reported.     

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.     

Raman spectroscopy of RuSr2(Eu1.5Ce0.5)Cu2O10 magneto-superconductor

Raman spectroscopy studies are reported for the RuSr₂Eu_1.5Ce_0.5Cu₂O₁₀ (Ru-1222) compound at various temperatures of 300, 250, 200 and 90 K. Three distinct vibrational bands: the first at 110, 140, and 160 cm⁻¹, the second at 295 and 347 cm⁻¹, and third one at 651 cm⁻¹ are seen in Raman spectra of the compound at room temperature. These bands are attached to the Cu atoms’ c-direction, the Ru atoms’ ab-plane stretching and Ru atoms’ c-direction anti-stretching modes. Below 200 K, an extra vibrational mode is also seen at 260 cm⁻¹. Also, with a decrease in temperature, though the Cu vibrational modes remain intact, the Ru atoms’ ab-plane stretching (295 cm⁻¹) and c-direction anti-stretching (651 cm⁻¹) modes shift gradually to higher wave number positions. The frequencies of modes at 260 and 651 cm⁻¹ showed anomalous softening and line-width broadening below 100 K that corroborates well with the spin ordering seen in susceptibility studies. The studied compound is a ferromagnetic superconductor with magnetic ordering of the Ru spins at 200 K and superconductivity below 30 K. A magnetic and electrical transport characterization of the compound is also presented briefly.