High pressure tuning of optical transitions in Mg[Pt(CN)4]·7H2O

Mg[Pt(CN)₄]·7H₂O belongs to the class of tetracyanoplatinates(II) which crystallize in columnar structures. In different M_x[Pt(CN)₄]·yH₂O (MCP) single crystals the in-chain Pt-Pt-distance R varies between 3.67 Å (NaCP) and 3.15 Å (MgCP). Two optical transitions can be observed in polarized emission with the electric field vector E either parallel or perpendicular to the columnar (c)-axis. Polarized emission spectra of MgCP are recorded under hydrostatic pressure up to p ≈ 18 kbar (at 295 K). The transition energy v?₆ can be tuned from 17,600 cm^-1 to about 12,000 cm^-1 (2.18-1.48 eV). The pressure induced red shift for the two transitions is: E 6 c: dv?₆/dp = -320±20 cm^-1/kbar, E ⊥ c: dv?_⊥/dp = -270±20 cm^-1/kbar. These values are discussed in the context of the known functional relationship (for ambient conditions) between v? and R.     

The adsorption of methylcyclopentane on Pt(1 1 1)

The adsorption of methylcyclopentane (MCP) on Pt(1 1 1) has been studied using the atom superposition and electron delocalization (ASED-MO) molecular orbital method. Results show a weak interaction with the metallic surface. The adsorption energy is rather independent of the adsorption site coordination number. We find that Pt 6s, 6p_z and 5d_z² orbitals are involved in the bonding with MCP. There is no bonding between the carbon ring and the Pt surface and the interaction comes from the hydrogen atoms to the surface.     

Rotational excitation of HD by collisions with He

The information theoretic surprisal analysis is employed to characterise the recent quantal close-coupling computations of rotational excitation rates by Green. The analysis is based on comparing the actual rates to the priors k⁰ which depend only on the temperature and the reduced “energy defect” ΔE_R/kT. The surprisal representation of the computed rates as k=k⁰ x exp (-I₀ - θ_R6ΔE_R6/kT is accurate throughout the temperature range considered by Green and is found to reduce in the low and high temperature limits to functional forms previously employed to characterise the rotational energy transfer rates in H₂.     

Beam quality of radial Gaussian Schell-model array beams

Taking the Rayleigh range z_R and the M²-factor as the characteristic parameters of beam quality, the beam quality of radial Gaussian Schell-model (GSM) array beams is studied. The analytical expressions for the z_R and the M²-factor of radial GSM array beams are derived. It is shown that for the superposition of the cross-spectral density function z_R is longer and the M²-factor is lower than that for the superposition of the intensity. For the two types of superposition, z_R increases and the M²-factor decreases with increase in beam coherence parameter, and both z_R and the M²-factor increase with increase in inverse radial fill-factor. For the superposition of the cross-spectral density function, z_R increases and the M²-factor decreases with increase in beam number, while for the superposition of the intensity both the z_R and M²-factor are independent of the beam number.     

Synthesis and luminescent study of diphosphine-Pt-disulfide complexes for OLED

Three novel diphosphine-Pt-disulfide complexes were synthesized and characterized by ¹H NMR, mass spectrometry and elemental analysis. As a diphosphine, 1,8-bis(diphenylphosphino)naphthalene (dppn), rac-2,2^′-bis(diphenylphosphino)-1,1^′-binaphthyl (dppbn), or 1,1^′-bis(diphenylphosphino)ferrocene (dppf) was employed and chelated to the Pt(II) center. As an anion, p-tolylsulfide (4-SC₆H₄CH₃) was incorporated to Pt(II) center subsequently, yielding (dppn)Pt(4-SC₆H₄CH₃)₂ (1), (dppbn)Pt(4-SC₆H₄CH₃)₂ (2), or (dppf)Pt(4-SC₆H₄CH₃)₂ (3). The photophysical properties of the resulting Pt complexes were investigated with UV–VIS spectroscopy, photoluminescence (PL) spectroscopy and transient PL. Charge Transfer absorptions between the metal and the ligand of 2 and 3 were observed at 320–350 nm in the UV–VIS spectra whereas such noticeable absorption was not observed in 1. The solid films of 1 and 3 showed luminescence at 600 and 580 nm, respectively, while that of 2 did not show emission at the room temperature. The complex 3 exhibited two excited state lifetimes, 23 and 125 ns, at room temperature, and the weighting factor for 125 ns state is only 10% of that for 23 ns one. It means that the prominent luminescence was fluorescence and the intersystem crossing through LS coupling is relatively weak.     

Behavior of Nitroxide Biradicals with Acetylene Bridges in Organic Solvents and Ionic Liquids

Intramolecular electron spin exchange (IESE) in two nitroxide biradicals, R₆–C≡C–C≡C–R₆ (1) and R₆–C≡C–p-C₆H₄–C≡C–R₆ (2), is studied as a function of temperature and solvent properties. The effect of molecular solvents and ionic liquids (ILs, [1-methyl-3-butylimidazolium]⁺[PF₆]^?, bmimPF₆, and [1-methyl-3-octylimidazolium]⁺[BF₄]^?, omimBF₄) on the IESE in magnetically diluted solutions is investigated. Changes in electron paramagnetic resonance spectra are analyzed and the thermodynamic parameters of these changes are calculated. Geometry optimization and D-tensor calculations of biradicals 1 and 2 were carried out on the DFT/UB3LYP/cc-pVdz and DFT/ROPBE/N07D levels of theory. The probable differences in biradical behavior are discussed.     

Determination of the Ni+-F- distance for square-planar and linear centers in LiF:Ni+ and NaF:Ni+

The distance R between Ni⁺ and the closest F^- anions for several square- planar and linear Ni⁺ centers observed in LiF and NaF has been derived from the isotropic superhyperfine constant A_s. R is smaller for linear than for square-planar centers according to Pauling's criteria. The knowledge of R for every square-planar center allows one to explain reasonably variations undergone by the experimental g_∥?g₀ values. Finally the present data reveal that the ionic radius of the unusual Ni⁺ ion is indeed quite close to that of Cu⁺.     

Evidence for the fröhlich collective mode in the one-dimensional conductor K2[Pt(CN)4] Br0.3 · 3H2O from far infrared reflection

Far infrared and infrared reflection measurements on single crystals of the one dimensional conductor K₂[Pt(CN)₄] Br_0.3 · 3H₂O have been performed at 4.2K, 62K and 300K for light polarized parallel (E6z) and perpendicular (E ? z) to the platinum chains. At 4.2K and 62K a strong structure is observed in the E6z spectrum near 40 cm^-1 which is not observable at 300K. This structure is interpreted as due to the Fröhlich collective 2q_F-phonon mode.     

Electrooptical properties of ferroelectric Gd2(MoO4)3

On the basis of the symmetry of the free energy function describing properly the transition of gadolinium molybdate into the ferroelectric state, macroscopic relations are derived for the spontaneous birefringence and for the temperature dependence of the electrooptic coefficientsz _ij . Since the transition parameters correspond to lattice vibrational modes with finitek, the resulting formulae differ considerably from those for classical ferroelectrics with transition parameterP. Experimental data are presented for the temperature dependence of freez ₆₃ andz ₄₁, clampedz ₆₃ and free permittivity for a multidomain and single domain crystal. These results and earlier data on spontaneous birefringence compare well with theory.     

Regular and chaotic motion of coupled rotators

We consider a classical Hamiltonian H = L_z+M_z+L_xM_x, where the components of L and M satisfy Poisson brackets similar to those of angular momenta. There are three constants of motion: H, L² and M². By studying Poincaré surfaces of section, we find that the motion is regular when L² or M² is very small or very large. It is chaotic when both L² and M² have intermediate values. The interest of this model lies in its quantization, which involves finite matrices only.     

Calculation of high-order rotational centrifugal-distortion matrix elements for a Hund's case (a) basis set

The derivation of explicit expressions for the Hund's case (a) matrix elements of R^2k is discussed, where R is the mechanical rotational angular momentum operator of the molecule. A recursion relation is developed that permits matrix elements of R^2k to be expressed in terms of those of R^2(k?1), thus affording a straightforward means of calculating the case (a) matrix elements of rotational centrifugal-distortion constants D_v, H_v, L_v, M_v, etc., to an arbitrarily high order. The explicit matrix elements of L_v are listed.     

Intensity measurements for the (2, 0) γ-band of O2, b1Σ+g−X3Σ-g

Quantitative intensity measurements have been made for the oxygen γ-band at 6280 Å. Intensities for 19 individual rotational lines of the P_P and P_Q branches and the intensity of the combined R_R and R_Q branches are reported. The band intensity, S^v′_v^″, is found to be 1.52±0.07 cm^-1km^-1atm^-1 (STP).     

Analysis of the ν3 band of 12CH3D at 7.6 μm

The previously reported (J. Mol. Spectrosc.68, 195–222 (1977)) study of the CH₃D spectrum occurring at 1033–1270 cm^?1 which was mainly concerned with the ν₆ fundamental has now been extended to cover the region 1270–1420 cm^?1. In all, 342 transitions belonging to the ν₃ band are now assigned. Both the ν₃ and ν₆ bands are processed simultaneously taking into account of the Coriolis interaction between them, and the fitting of all the experimental data led to 21 significant spectroscopic constants for the states v₆= 1 and v₃ = 1 of CH₃D.     

Infrared reflection absorption spectral study for CO adsorption on Pd/Pt(1 1 1) bimetallic surfaces

Infrared reflection absorption spectroscopy (IRRAS) was used to investigate carbon monoxide (CO) adsorption on 0.15 nm-thick-0.6 nm-thick Pd-deposited Pt(1 1 1) bimetallic surfaces: Pd_x/Pt(1 1 1) (where x is the Pd thickness in nanometers) fabricated using molecular beam epitaxial method at substrate temperatures of 343 K, 473 K, and 673 K. Reflection high-energy electron diffraction (RHEED) measurements for Pd_0.15-0.6 nm/Pt(1 1 1) surfaces fabricated at 343 K showed that Pd grows epitaxially on a clean Pt(1 1 1), having an almost identical lattice constant of Pt(1 1 1). The 1.0 L CO exposure to the clean Pt(1 1 1) at room temperature yielded linearly bonded and bridge-bonded CO-Pt bands at 2093 and 1855 cm⁻¹. The CO-Pt band intensities for the CO-exposed Pd_x/Pt(1 1 1) surfaces decreased with increasing Pd thickness. For Pd_0.3 nm/Pt(1 1 1) deposited at 343 K, the 1933 cm⁻¹ band caused by bridge-bonded CO-Pd enhanced the spectral intensity. The linear-bonded CO-Pt band (2090 cm⁻¹) almost disappeared and the bridge-bonded CO-Pd band dominated the spectra for Pd_0.6 nm/Pt(1 1 1). With increasing substrate temperature during the Pd depositions, the relative band intensities of the CO-Pt/CO-Pd increased. For the Pd_0.3 nm/Pt(1 1 1) deposited at 673 K, the linear-bonded CO-Pt and bridge-bonded CO-Pd bands are located respectively at 2071 and 1928 cm⁻¹. The temperature-programmed desorption (TPD) spectrum for the 673 K-deposited Pd_0.3 nm/Pt(1 1 1) showed that a desorption signal for the adsorbed CO on the Pt sites decreased in intensity and shifted ca. 20 K to a lower temperature than those for the clean Pt(1 1 1). We discuss the CO adsorption behavior on well-defined Pd-deposited Pt(1 1 1) bimetallic surfaces.     

Hyperfine structure investigations of some odd levels of Co I by level crossing and optical methods

Using the level crossing technique the ratios and absolute values of the hyperfine structure (hfs) constants of the levelsz ⁴F_9/2 andz ⁴F_7/2 of the configuration 3d ⁷4s4p of Co I were measured:z ⁴ F _9/2: ¦A¦=(811±12)MHz; ¦B¦=(48±93) MHz;B/A=?0.06±0.11 A>0; B<0z ⁴ F _7/2: ¦A¦ = (659 ±11)MHz; ¦B¦=(33±84)MHz;B/A=?0.05±0.13 A>0; B<0. In addition the hfs constants of three other excited levels of Co I could be determined by optical methods:z ⁴ F _9/2:A=525±26 MHz;B=200 MHzy ⁴ F _9/2:A=300±30 MHz;B=?500 MHzy ⁴ G _11/2:A=315±20 MHz;B=400 MHz. The experimental results are compared with known experimental and also with theoretical values which where calculated using the parametric potential method.     

Evidence for shape coexistence in186Pt

High-spin states in¹⁸⁶Pt have been populated by the¹⁸⁸Os (α, 6n) reaction and were investigated with the OSIRIS spectrometer. A shape coexistence at high spins was established in the nucleus¹⁸⁶Pt, which lies on the border between light prolate and heavy oblate Pt nuclei. Two bands corresponding to predominantly prolate shapes and one band of predominantly oblate shape have been observed. For prolate shapes a (π h _9/2)² alignment and for oblate shapesa (vi _13/2)² alignment has been found.     

High-resolution stimulated Raman gain spectrum of the ν1 band of SF6

We report rotationally resolved stimulated Raman gain spectra of the ν₁ band of SF₆. The fundamental band exhibits a rigid-rotor type spectrum that is readily fit with a band origin of Δα = 774.5445 and a single rotational term Δβ = ?1.10376 × 10^?4 cm^?1. We also observed and analyzed the ν₁ + ν₆ hotband with band origin at 774.1820 cm^?1. With an experimental resolution of 0.0024 cm^?1 there is no evidence for centrifugal distortion or tensor splitting in either band, although the ν₁ + ν₆ band does exhibit first-order Coriolis splitting as expected.     

Beam quality of truncated laser beams with amplitude modulations and phase fluctuations in turbulence

The closed-form expressions for the Rayleigh range z_R and the M²-factor of truncated laser beams with amplitude modulations (AMs) and phase fluctuations (PFs) in turbulence are derived, and the beam quality is studied by taking the z_R and the M²-factor as the characteristic parameters of beam quality. The M²-factor of truncated laser beams with AMs and PFs is always larger than that of truncated Gaussian beams both in free space and in turbulence. However, in turbulence the beam quality of truncated laser beams with AMs and PFs may be better than that of truncated Gaussian beams if the z_R is taken as the characteristic parameter of beam quality. For laser beams with AMs and PFs in turbulence, the beam quality expressed in terms of z_R is consistent with that in terms of the M²-factor versus the phase fluctuation parameter α, but not versus the intensity modulation parameter σ_A. The beam quality of truncated laser beams with AMs and PFs is less sensitive to turbulence than that of truncated Gaussian beams. The beam quality of laser beams with smaller α and larger σ_A is less affected by turbulence than those with larger α and smaller σ_A.     

The magnetooptical properties of InSe near the band gap

We have studied the magnetooptical properties of InSe near the band gap by wavelength modulation spectroscopy at 10 K with the electric vectorE perpendicular to theC-axis of the crystal. For the first time, Landau levels have been observed from which we obtain the reduced effective mass perpendicular to $\overrightarrow{C}$, μ_⊥ = (0.090 ± 0.010)m₀. The n = 1, 2 and 3 exciton lines along with a diamagnetic shift of the n = 1 level have been resolved from which we evaluate the Rydberg constant R = 15.0 ± 0.5 meV, the diamagnetic shift σ₁ = 14 ± 2 meV/(kG)² and ε_⊥ε_∥ = 81 ± 8. Evidence of the presence of the γ and ε polytypes in the sample due to stacking faults is given.