Observations of four-wave mixing processes in barium vapour

Emission at fifty discrete wavelengths is observed when Ba I is excited by two laser beams, a dye laser tuned to the λ 7911 Å intercombination line, 6s²¹S₀-6s6p ³P₁ and a ruby laser. The wavelengths range from 2312 Å to 8027 Å. Most of the emission lines can be attributed to four-wave mixing processes in barium.     

The vibrational structure of the electronic spectra of quinoxaline in shpolskii-type hydrocarbon matrices

Quasilinear spectrum of the S₁(n, π¹, ¹B₁) ← S₀ transition of quinoxaline in crystalline methylcyclohexane matrix and quasilinear phosphorescence spectra of quinoxaline in high- and low-temperature modifications of isooctane matrix were obtained at 77 K. The results of a full vibrational analysis of the spectra are presented and discussed. The diffuseness of the absorption spectrum in the range 3200-2900 Å is ascribed essentially to a small energy gap between the S₂ and S₃ states. The activity of out-of-plane vibration, 865 cm^-1, in the phosphorescence and the influence of matrices on the structure of the spectra suggest the possibility of out-of-plane distortion of the quinoxaline molecule in the T₁ state.     

Relative photodissociation cross-section of NaCs molecule,using argon ion laser lines

Laser-induced photodissociation of NaCs molecule has been observed when a mixture of Na and Cs metal vapour in a glass cell was irradiated by most of the lines of an argon ion laser. The photodissociation results in the 3P state of Na atoms which is correlated with theF ¹Σ⁺ and G¹π molecular states of NaCs. Distribution of photofragments over fine structure components 3² P _3/2 and 3² P _1/2 of Na has been studied. The ratio of intensity ofD ₂ line (5890 Å) toD ₁ line (5896 Å) of Na varies from around 2 at 5145 Å to about 3.5 at 4579 Å. The relative photodissociation cross-section increases monotonically as the wave-length of laser light decreases from 5145 Å to 4579 Å. It is seen that the 4579 Å photon is about 200 times more effective than the 5145 Å photon in causing the photoreaction NaCs + (Ar⁺ photon) → Na*(3P) + Cs(6S).     

M-dependence of collisional transfer of rotational energy in OCS mixtures

Collision-induced transitions between rotational levels of OCS in the ground vibrational state have been investigated by steady-state microwave double resonance, with the M sublevels separated by a Stark field. The (2 ← 1)_P-(1 ← 0)_S, (3 ← 2)_P-(1 ← 0)_S, and (4 ← 3)_P-(1 ← 0)_S systems have been studied for pure OCS and for mixtures with excess CH₃OH, He, and H₂. For four-level systems having dipolar connections (ΔJ = 1; ΔM = 0, ± 1; parity ± ? ?) between pump and signal levels, it is found for OCS and the OCS-CH₃OH mixture that the dipole-type ΔJ = 1 transitions always dominate the collisional transfer, but for the OCS-He and OCS-H₂ mixtures that ΔJ = 2 quadrupole-type transitions are dominant. For all four collision partners, significant ΔJ = 2 and ΔJ = 3 collisional transfer is observed in some systems, indicating the presence of high-order terms in the collisional interaction.     

Enhancement of spectral intensities of mercury triplet lines in longitudinal magnetic field

The variation of intensity of the spectral lines of the triplet series of mercury namely (7³ S ₁ → 6³ P ₀₁₂) (λ5461 Å,λ 4358 Å,λ 4047 Å) in the presence of a longitudinal magnetic field between zero and 2000 gauss has been investigated. The effect of magnetic field is found to be different as regards the variation of intensity and the occurrence of maxima in the three lines. These variations can be explained by considering the reabsorption of the spectral lines. A mathematical theory has been presented and an expression for (I _ul ) _B /I _ul has been deduced where (I _ul ) _B and (I _ul ) are the intensities of the lines with and without the magnetic field. The experimental results agree fairly well with the theoretical model.     

Diode laser spectroscopy of the ν3 band region of four isotopic forms of CS2

The diole laser spectrum of a natural sample of the linear molecule, CS₂, has been measured in the region 1450–1550 cm^?1. An absolute frequency calibration of approximately 0.001 cm^?1 was achieved by measuring CS₂ absorption lines relative to those of H₂O and HDO and using the absolute wave numbers of Guelachvili [J. Opt. Soc. Amer., 73, 137–150 (1983)]. Band constants were determined for the following: C³²S₂; (0, 0, 1) ← (0, 0, 0), (0, 1¹, 1) ← (0, 1¹, 0), (0, 2^0,2, 1) ← (0, 2^0,2, 0), (1, 0, 1) ← (1, 0, 0); ³⁴SC³²S; (0, 0, 1) ← (0, 0, 0): ³³SC³²S; (0, 0, 1) ← (0, 0, 0): ¹³C³²S₂; (0, 0, 1) ← (0, 0, 0).     

Estimate of the wavelengths for the first and second resonance lines in the francium I spectra

Relativistic self-consistent-field wavefunctions have been used to calculate one-electron eigenvalues for the ground s-state, the first and the second excited p-states of Sr II, Cs I, Ba II, Fr I and Ra II. When knowing the difference between the experimental energies and the theoretical ones for Sr II, Cs I, Ba II and Ra II the wavelengths for the first and second resonance lines in Fr I have been estimated with the following result: λ(7²P_1/2? 7²S_1/2)=812±10) nm λ(7²P_3/2? 7²S_1/2)=719±10) nm λ(8²P_1/2? 7²S_1/2)=433±5) nm λ(8²P_3/2? 7²S_1/2)=423±5) nm     

Broadening and shift of neutral chromium absorption lines by various perturbing gases

The broadening and shift of the absorption lines (a⁷S-z⁷P°, a⁷S-y⁷P° and a⁵S-z⁵P°) of the neutral chromium atom were observed at various temperatures (1500–1800 K) and densities (0.24-3.2x 10¹⁹/cm³) of foreign perturbers (He, Ar, N₂, H₂). The dependence of width and shift on temperature and density was studied. The collisional broadening and shift rates were determined from the profile measurements. The results are interpreted in terms of the Lindholm-Foley interaction potential between radiating atom and perturbers. Semi-quantitative agreement of theory and experiment was found in some cases for the temperature dependence of width and shift and for the differences of attractive constants ΔC₆ between upper and lower states of chromium lines.     

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.     

The microwave spectrum of germyl isocyanate,a quasi-symmetric top

The microwave spectrum of germyl isocyanate in the K, P, and R bands (12.4–40.0 GHz) has been investigated using natural isotopic samples and samples containing specific germanium isotopes, mass numbers 72 and 74, and samples containing GeD₃ groups. The very complex spectrum is analyzed as that of a quasi-symmetric top, in which the skeletal bending motion has an energy maximum at the linear configuration; the height of the maximum is some 339 cm⁻¹. Many vibrational states of the two-dimensional bend lie close in energy, resulting in strong interactions between rotational levels of different vibrational states. The program used for the analysis has been used previously to account for similar spectra of methyl and silyl isocyanates and methyl isothiocyanate; the behavior of the germyl compound is more like that of the methyl isocyanate than that of the silyl compound, where the height of the maximum is much less. Although we did not include centrifugal distortion operators in the Hamiltonian the program successfully predicts k = 0 line positions in J + 1 ← J bunches with J up to 9, using only lines in the J = 3 bunch to define the parameters of the model, which include the height of the hump, the bend angle of the skeleton at the energy minimum (142.18(5)°), the force constant for the bending motion at the minimum (0.1094(7) mdyn Å), and the GeN bondlength at equilibrium (1.8257(5) Å). The threefold barrier to internal rotation of the GeH₃ group at the equilibrium position is about 3 cm⁻¹, much lower than the value found for methyl isocyanate. The fit to the observations, about 100 lines in the 4 ← 3 bunch, is improved by allowing for a variation in the GeN bondlength as the bend angle changes. The quality of the least-squares fit corresponds to an estimated standard deviation for an observation of about 2 MHz, but not all observed lines can be accounted for precisely, showing that additional interactions are involved that are not yet included in the model.     

Ba原子6s6p1P1←6s6s1S0跃迁的光腔衰荡光谱

建立了一套光腔衰荡原子束吸收光谱测量装置,并对Ba原子的6s6p¹P₁←6s6s¹S₀吸收谱线用光腔衰荡光谱方法进行了测量,得到了Ba原子在553.548nm不同温度下的吸收谱线线型.实验结果表明,该装置测量吸收灵敏度达到6×10^-7. 关键词： 光腔衰荡 吸收光谱 Ba原子     

Optical absorption spectra of s2 impurity ions in aqueous halide ion glasses

The optical absorption bands of aqueous 0·05 M Sn²⁺ in 7 M LiI at 77°K appear at 361, 352, 325, 310, 300, 292 and 262 nm. They are considered to be the A₁, A₂, B, C₁, C₂, C₃ and D′ bands since the positions and relative intensities lie within the range of those bands for Sn²⁺-doped alkali iodide crystals. Upon warming the glass there is an uncorrelated increase in the B band and a decrease in the A₁ band. In 3·6, 4·1, 4·6 and 5·1 M CaCl₂ glasses with 5×10^?3 M Sn²⁺ the A₁ and A₂ bands show uncorrelated increases with increasing concentration of Cl^?. Comparable observations are reported for Pb²⁺-doped glasses of lithium halides and CaI₂. In general the spectra of the Sn²⁺- and Pb²⁺-doped glasses correlate well with those of the corresponding crystal systems. The effect of temperature and halide-ion concentration are attributed to shifts in chemical equilibria among the well-known halo complexes, MX_n^2?n MX_n?1^1?n+X^?, each having a characteristic, absorption and emission. Absorptions may be attributed to M²⁺(³P₁ ← ¹S₀) and M²⁺(¹P₁ ← ¹S₀) in the complex, shifted by partially covalent bonding of n halide ions.     

Magnetic rotation observation of the C2b3Σg− ← a3Πu transition using a color center laser

The magnetic rotation observation of the C₂b³Σ_g^? ← a³Π_u Ballik-Ramsay system using a color center laser is reported. This is the first detection of this system in absorption. Three bands, 0 ← 1, 1 ← 2, and 2 ← 3, were identified in the spectral range 3650–4030 cm^?1. The last two bands were observed for the first time. In magnetic rotation many satellite lines (ΔN ≠ ΔJ) which would be very weak in normal absorption have been observed with intensity comparable to the main branch lines. This permits a slight improvement in the accuracy of some of the fine structure constants. A variety of lineshapes are observed for the various branches by magnetic rotation. Because the b³Σ_g^? fine structure is small, giving a partial overlap, the peak frequency of a magnetic rotation signal usually does not correspond to the center frequency of the normal absorption signal of that transition. A computer program has been written to predict magnetic rotation lineshapes and obtain the peak frequency displacements. Various observed and calculated lineshapes are displayed and compared.     

Measured lifetimes in mercury using the photon-photon delayed coincidence technique

The photon-photon delayed coincidence technique has been used to measure the 6³P₁, 7³S₁, and 7¹S₀ level lifetimes in mercury atoms. The measured mean lifetimes are 6³P₁(116±5) ns, 7³S₁(7.7±0.4) ns and 7¹S₀(30.5±4.3) ns, respectively.     

On pair-absorption in intrinsic vapours

The bound-state pair-absorption bands Cs(6² S _1/2)+Cs(6² S _1/2)+h v→Cs(5² D _5/2,3/2) +Cs(6² P _1/2) and the K — K continuum-state pair-absorptions in the wavelength region 2,350≦λ≦2,850 Å have been investigated experimentally. In the case of the bound-state pair-absorption bands a theoretical approach for the absorption cross section at the band centre is given which is in good agreement with the experimental observation. Differences between our and the theoretical formulas given by the Stanford group are discussed.     

Action d'un champ magnetique sur le taux de polarisation de la raie interdite 2655,6 Å (61S0-63P0) du mercure

The forbidden radiation 2655.6 Å (6¹S₀-6³P₀) emitted by the odd isotopes of mercury is polarized in a magnetic field, even if the atoms are isotropically excited. The degree of polarization has been calculated for the case of ¹⁹⁹Hg. The experimental results agree with the theoretical predictions.     

The near-ultraviolet spectrum of diacetylene trapped in solid argon at 9 K

The absorption spectra of normal and deuterated diacetylene trapped in solid argon at 9 K were investigated in the near-ultraviolet region between 2000 and 3000 Å. The vibrational structure observed at low temperature for the band system at 2448 Å, which was previously reported by Haink and Jungen in the gas phase, and identified as a ¹Δ_u ← X¹Σ_g⁺ transition, was analyzed. A comparison between the spectra for C₄H₂ and C₄D₂ suggests some revisions in the upper-state vibrational assignments. The possibility that the upper state assumes a C_2htrans configuration of ¹A_u symmetry is examined. The matrix spectra also appear to indicate that the absorption spectrum observed at 2576 Å in the gas phase and which has been assigned to a ¹Σ_u^? ← X¹Σ_g⁺ transition may not originate in the ground state of C₄H₂.     

Structure of 4,4′-butane-(1,4,7-three-p-tolylsulphonyl-1,4,7-three amine) diphthalonitrile

Abstract

The crystal structure of the title compound, C₄₁ H₃₅ N₇ O₆ S₃ was determined as monoclinic by single crystal X-Ray diffraction technique. The molecular structure was identified by IR, ¹H-NMR, ¹³C-NMR and elemental analysis. The crystal parameters of this compound are as follows: monoclinic P 2 1/n, a = 12.694(2) Å, b = 26.204(2) Å, c = 13.005(2) Å, β = 102.95(2)°, V = 4216.02(1) Å.³, Z = 4, Dx = 1.289 g/cm³, F(000) = 1704, λ (MoKα) = 0.71070 Å, μ = 0.2 mm^?1. The structure was solved by SHELXS-97 and refined by SHELXL-97. R = 0.06 for 3178 observed reflections with I > 2σ (I).     

Submillimeter spectrum and spectroscopic constants of the arsine molecule in the ground vibrational state

The submillimeter spectrum of the arsine molecule, AsH₃, of both the allowed R-branch transitions (J + 1 ← J, J = 0, 1, 2, 3) and forbidden transitions of the Q branches, |K| = 4 ← 7, 5 ← 8, 6 ← 9, is investigated in the frequency range from 220 to 900 GHz. Weak absorption lines were observed by using the spectrometer RAD with sensitivity increased by a nontunable cavity cell. On the basis of the results obtained and microwave data available in the literature the rotational spectrum of the arsine molecule in the ground state is analyzed.     

Energy transfer between Eu3+ ions in a lattice with two different crystallographic sites: Y2O3:Eu3+, Gd2O3:Eu3+ and Eu2O3

The Eu³⁺ ion occupies two different crystallographic sites in (Y_1−xEu_x)₂O₃ and (Gd_1−xEu_x)₂O₃, with site symmetry S₆ and C₂. Energy transfer over more than 7 Å occurs from Eu³⁺ (S₆) ions to Eu³⁺ (C₂) ions. This is shown to be a direct one-phonon assisted process, in combination with a one-site resonant two-phonon assisted process at higher temperatures. For x = 1 there is energy migration over the Eu³⁺ (C₂) sublattice to quenching impurities. The presence of cooperative absorption points to superexchange interaction between the Eu³⁺ ions.