Temperature-dependent light scattering from magnetic excitons in TlCoF3

Raman spectra of antiferromagnetic thallium cobaltous fluoride have been obtained with 4579A argon ion laser excitation at temperatures from 4°K to T_N = 94 ± 2°K. The features observed consist of six Co²⁺ excitons ranging in energy from 325 to 1070 cm^-1, at two-magnon peak with low-temperature energy of 315 cm^-1, and a one-magnon feature whose 4°K energy is 37 cm^-1. The energy and linewidth of the one-magnon scattering has been measured from 4°K to about 0.8 T_N; it is found that the magnon becomes critically damped at about 0.8 T_N, in good agreement with our previous observations on RbCoF₃. The Co²⁺ excitons observed at 325, 380, 410, 730 (weak), 960, and 1070 cm^-1 agree in energy quite well with the KCoF₃ levels calculated by Buyers, Holden et al. as 340, 400, 467, 767, 967 and 1050 cm^-1.     

Influence of interchain coupling on the one-dimensional magnon raman spectrum of CsCoBr3

Light scattering from magnons in CsCoBr₃ has been measured for temperatures well below the upper antiferromagnetic 3D ordering temperature of T^l_N = 28 K. These experiments reveal multiple magnon features of energies in the range 90 to 170 cm^-1 similar to those found in CsCoCl₃ but previously unobserved for the bromide. Prominent features in the spectrum and their temperature dependence are described in terms of a recent theory by Shiba. Other, weaker features are explained by a simple extension of the theory to include fluctuations. A new band is observed at 178 cm^-1, whose intensity drops sharply prior to the lower 3D ordering transition at T^∥_N = 10 K. This band is assigned to magnon-phonon combination scattering.     

Influence of interchain coupling on the one-dimensional magnon Raman spectrum of CsCoBr3

Light scattering from magnons in CsCoBr₃ has been measured for temperatures well below the upper antiferromagnetic 3D ordering temperature of T^l_N = 28 K. These experiments reveal multiple magnon features of energies in the range 90 to 170 cm^-1 similar to those found in CsCoCl₃ but previously unobserved for the bromide. Prominent features in the spectrum and their temperature dependence are described in terms of a recent theory by Shiba. Other, weaker features are explained by a simple extension of the theory to include fluctuations. A new band is observed at 178 cm^-1, whose intensity drops sharply prior to the lower 3D ordering transition at T^l_N = 10 K. This band is assigned to magnon-phonon combination scattering.     

Temperature dependence of light scattering by the one-magnon excitation in NiF2 crystals

We have studied the one-magnon excitation in NiF₂ crystals by the method of right-angle light scattering from 1 to 73°K. The temperature dependence of frequency and line width agrees very well with previous far infrared absorption data. The temperature dependence of the integrated intensity follows the theoretical prediction but deviates from the previous far infrared data.     

Optical investigation of DyFeO3

Optical absorption spectra of DyFeO₃ have been investigated at 1.2≦T≦4.2 °K, andT=77 °K From the temperature dependent lineshift a Néel temperature ofT _N=(3.8±0.5) °K is deduced for the dysprosium sublattices. The groundstate splitting due to the iron-dysprosium interactions is about 1.5 cm^?1 and due to the dysprosiumdysprosium interactions (5.0±1.4) cm^?1. Zeeman studies give the magnetic moment of the dysprosium ions asμ=(9.2±1.0)μ _B.     

Comment on the intensity and the temperature dependence of the nitrogen-broadened half-width of the P(6) line in the CO fundamental

The recent line-center absorption coefficient measurements on the P(6) line of the CO fundamental have been shown to be consistent with S_v(T) = 273(273/T)cm^-2atm^-1 and γ⁰(T) = 0.0652(300/T)^0.66 for the absolute intensity of the band and the nitrogen-broadened line width in the temperature range 300–800°K.     

Measurement at different temperatures of absolute intensities,line half-widths,and broadening by Ar and N2 for the 3001II←0000 band of CO2

Absolute intensities, self-broadening coefficients, and foreign-gas broadening by Ar and N₂ were measured at temperatures of 197, 233 and 294 K for the 30⁰1_II←00⁰0 band of CO₂ at 6348 cm^-1. Also, the intensity parameters and total band intensity were calculated. We obtained for the vibration-rotation interaction factor the value F(m) = 1 + (0.26 ± 0.06) × 10^-2m + (0.92 ±0.32 × 10^-4 m²; for the purely vibrational transition moment, we found ¦R₀₀₀₀^3001_II¦к(0.4351 ± 0.0014)()10^b3 debye; and, for the total band intensity at STP conditions, S_band(30⁰1_II←00⁰0)_STP = 1255 ± 9 cm^-1 km^-1 atm^-1.Self-broadening coefficients at 197 and 294 K were also measured, as well as broadening by Ar and N₂. Foreign-gas-broadening efficiencies (Ar and N₂) were determined. Finally, a comparison is made with measurements by other authors and with theoretically calculated values.     

Tunable diode laser measurements of spectral parameters of HCN at room temperature

A tunable infrared diode laser was used to record 17 fully resolved vibration-rotation transitions in the v₁ fundamental band of HCN at 3μ. The experiments were conducted in an absorption cell on room temperature mixtures of HCN diluted by N₂ and Ar. The v₁ fundamental band strength of HCN was determined to be 267±8 cm^-2 atm^-1 at 273.2 K. Small but significant reductions in the residual errors were obtained by using the Galatry profile rather than the Voigt profile to fit the experimentally recorded line shapes. Collisional broadening and narrowing parameters were determined simultaneously from Galatry profile fits to the data. The collision-broadened linewidths of HCN lines in N₂ and Ar were determined as a function of rotational quantum number of transitions ranging from P(14) to R(14) (3268.22-3353.29 cm^-1). The optical diffusion coefficients of HCN in N₂ and Ar at 300 K were determined from the collisional narrowing parameters and were 0.074±0.01 and 0.016±0.03 cm²s^-1 respectively.     

Raman scattering from magnons in CoCl2 and FeCl2

One-magnon Raman scattering has been observed in the metamagnets CoCl₂ and FeCl₂. The k = 0 magnon energies are 16 ± 1 cm^-1 at 21 K and 16.4 ± 0.4 cm^-1 at 12 K, respectively and these values are in good agreement with previous AFMR and neutron scattering results. A search for two-magnon scattering in both compounds was unsuccessful, largely because of masking from nearby first-order phonons and a weak temperature dependent broad band at 140 cm^-1 in CoCl₂, which is assigned to two-phonon scattering from acoustic phonons.     

Hall effect in α-RuCl3

The Hall effect measurements performed in the layer compound α-RuCl₃ show that, in the sheets perpendicular to the c-axis, μ(300 K) ? 0.2 cm²V sec^?1; the temperature dependence of μ appears to be μ(T) = μ₀T^-n, with n = 2.3 ± 0.1, in the 180–320 K range. The transport appears to be due to electrons that move with a band type of mechanism, the main scattering process being due to the homopolar high energy phonons which modulate the thickness of the layers.     

Intensity and line-width measurements of the NO fundamental by infrared molecular absorption spectrometry

The integrated intensity of the fundamental vibration-rotation band of NO and the pressure-broadening parameters of NO with various foreign gases have been determined at room temperature by measuring the resonance absorption of the infrared emission line of the NO fundamental. The Hg photo-sensitized vibrational excitation of NO was utilized to obtain a light source for the NO fundamental. in which the individual rotational lines could be described in terms of the Doppler line profile at room temperature. The total band intensity was found to be 122 ± 6 cm^-2 atm^-1, and the collision-broadened full-widths at half maximum in CO₂, N₂, Ar, H₂ and He gases were 0.10, 0.086, 0.059, 0.086 and 0.078 cm^-1 atm^-1, respectively.     

Intensity and transmission measurements in the ν3-fundamental of N2O at low temperatures

Spectral transmission of i.r. radiation through the nitrogen-broadened lines of the υ₃-fundamental of N₂O has been measured at 154°, 202° and 300°K. A value of S⁰_v = 1411±54 cm^-2atm^-1 at S.T.P. has been obtained for the combined strength of the ν₃ and ν₂¹+ν₃?ν₂¹ bands using the Wilson-Wells-Penner-Weber method. This value for S_v, the relative intensity calculations of Gray Young, the room-temperature data of Toth for nitrogen-broadened half-widths in the ν₁+ν₃ and 2ν₂⁰+ν₃ bands and the T^-0.75 variation of line width with temperature proposed by Varanasi and Sarangi are shown to yield excellent agreement between the measured and computed spectral transmittance throughout the band.     

Raman scattering by optical phonons and polaritons in CuCl

We present data on forward and backward scattering in CuCl at liquid N₂ temperature. Peaks at 146 and 172 cm^-1 which appear in both forward and backward scattering spectra are attributed to other than first order scattering by optical phonons. The data on polarition scattering indicate that the atomic displacement contribution to the scattering by TO phonons is rather small. From the experimentally determined polarition dispersion curve we obtain a value of 174 ±2.5 cm^-1 for ω_T and a value of 5.3 for ?_S.     

Spektroskopische Untersuchungen an DyAsO4

DyAsO₄ undergoes a crystallographic phase transition atT _D=11.2K which is induced by a cooperative Jahn-Teller-effect. As deduced from the optical absorption spectra the distance between the two lowest lying Kramers doublets of the Dy³⁺ ion is increased from (6.1±0.5) cm^?1 aboveT _D to (25.0±0.5) cm^?1 at 4.2 K. BelowT _D the splitting factor of the lowest doublet becomes nearly uniaxial with a maximum value ofg _b =17.5±1.0 along the crystallographicb-axis. AtT _N=2.44 K the crystals order antiferromagnetically. The absorption lines of Er³⁺ ions in DyAsO₄ show already a splitting immediately belowT _D which is explained by magnetic short range ordering of the Dy³⁺ ions in the temperature rangeT _{N D} .     

Shock-tube study of HCN self-broadening and broadening by argon for the P(10) line of the ν1 band at 3 μm

A tunable infrared diode laser was used to measure the fully resolved absorption line shape of the P(10) line in the ν₁ band (10°0–00°0) of HCN for shock-heated mixtures of HCN-Ar at temperatures of 1000, 1500 and 2000 K. The temperature dependence of the collision-broadening coefficients 2γ (cm^-1 atm^-1, FWHM) were inferred for both self-broadening and broadening by argon. For the assumed form 2γ = 2γ₀(T₀/T)ⁿ the exponent n was determined to be 0.63 ± 0.06 with 2γ₀ = 0.11 cm^-1atm^-1 and T₀ = 300 K for argon-broadening in the range 300 < T < 2000 K, and 1.2 ± 0.6 with 2γ₀ = 0.68 cm^-1atm^-1 and T₀ = 1000 K for self-broadening in the range 1000 < T < 2000 K.     

Measurements of the HCN ν3 band broadened by N2

N₂-broadened halfwidths have been measured for 51 absorption lines belonging to the ν₃ fundamental band of hydrogen cyanide (¹H¹²C¹⁴N) near 3311 cm^?1. The data were recorded at room temperature using a Fourier transform spectrometer with a nominal resolution of 0.06 cm^?1. A nonlinear least-squares spectral-fitting procedure was used to obtain both line intensities and collision-broadened halfwidths from scans recorded at several different pressures. The N₂-broadened halfwidths, determined for all lines with J ≤ 25 in both the P and R branches of the band, show the expected distribution with J for broadening by a nonpolar gas. The halfwidth values range from approximately 0.17 cm^?1 atm^?1 near the band center to 0.11 cm^?1 atm^?1 for high-J lines. The band intensity for the ν₃ fundamental derived from these measurements is 236.2 ± 9.5 cm^?2 atm^?1 at 296 K, and empirical coefficients for the vibration-rotation interaction F-factor were also determined.     

Measurement of intensities of multiplets in the 2ν3-band of methane at low temperatures

The integrated intensities of the multiplets P(1)–P(10), R(0)–R(9), and of the Q-branch in the 2ν₃-band of ¹²CH₄ have been measured at 102°K, 152°K, 202°K, 251°K, and 300°K. Comparison of our data with theoretical line strengths confirms, at all of the temperatures mentioned, the intensity anomalies observed by Margolis⁽⁵⁾ for lines in this band. The integrated intensity of the 2ν₃-band is found to be S_v = (1·76±-0·04)(300/T (°K)) cm^?2 atm^?1.     

Intensity measurements in the v4-fundamental of methane

The absolute intensities of all the J-multiplets between R(13) at 1375cm^-1 and P(12) at 1225 cm^-1, in the v₄-fundamental of ¹²CH₄, have been measured at 300°K. Our values are consistent with published band-intensity measurements and also with the theoretical line strength tabulation by Fox. Spectral transmittance computation using a Lorentz line shape with a hydrogen-broadened half-width of 0.075 cm^-1 atm^-1 at 300°K for all the lines in the band is in excellent agreement with our experimental data measured with a spectral resolution of 0.2 cm^-1. Our best estimate for the absolute intensity of the band is 145±8 cm^-2 atm^-1 at STP.     

Absolute intensities and pressure broadening coefficients measured at different temperatures for the 201II ← 000 band of 12C16O2 at 4978cm-1

Absolute line intensities and self-broadening coefficients have been measured at 197° and 294°K for the 201_II ← 000 band of ¹²C¹⁶O₂ at about 4978cm^-1. The vibration-rotation factor (F_VR), the purely vibrational transition moment (∣R(O)∣), and the integrated band intensity (S_band) are deduced from the measurements. The results are: F_VR(m)=1+(0.24±0.08)x10^-4m+(0.55+0.21)x10^-4m², ∣R(O)∣= (4.340±0.008x10^-3 debye, S_band=96372±190cm^-1km^-1atm^-1_STP. The results for self-broadening coefficients, as well as for individual vibration-rotation lines, are presented in the text.     

High resolution measurements of the line positions and strengths of the 2ν2 band of H2CO

Spectra of the 2ν₂ band of formaldehyde have been obtained with high resolution (0.035 cm^?1). Measurements were made with path lengths of 8, 16, and 24 m and at sample pressures from 0.1 to 0.3 mm Hg at room temperature (～296°K). From these data, the following constants were determined for the 2ν₂ band in wavenumber units: v₀=3471.718±0.004,A=9.3958±030013,B=1.28100±0.00024,C=1.11662±0.00024, Tbbb=-12.8±0.5×10^-6,Taabb=60±5×10^-6. The line strengths were also obtained from the data. The strengths were analyzed to determine the band strength and the rotational factors. At 296°K, the strength of the 2ν₂ band was found to be 15.5 ± 0.9 cm^?1/(cm·atm).