Infrared chemiluminescence in the reactions of 0.45 eV hydrogen atoms with Cl2, SCl2 and PCl3

Infrared chemiluminescence from HCl has been observed in “arrested relaxation” experiments to yield vibrational and rotational distributions from the reactions $\text{H}$+Cl₂, SCl₂ and PCl₃, where $\text{H}$ denotes hydrogen atoms with translational energy of 0.45 eV. The following relative populations were determined: N_v-1: N_v-2: N_v-3: N_v-4: N_v-5: N_v-6 = 0.89:1.00:0.84:0.47:0.26:0.11 for $\text{H}$+Cl₂: N_v-1: N_v-2: N_v-3: N_v-4: N_v-5: N_v-6 = 0.80:1.00:0.72:0.48:0.24:0.10 for $\text{H}$+SCl₂: N_v-1: N_v-2: N_v-3: N_v-4: N_v-5 = 0.79:1.00:0.88:0.36:0.14 for H+PCl₃. In all three reaction systems the chemiluminescence was attributed to the primary chlorine abstraction. Comparison with the results of the thermal processes (0.04 eV hydrogen atoms) led to the following conclusions: for H+Cl₂ the excess of translational energy is transformed into translational product energy and rotational energy of the molecule HCl; for H+SCl₂ the excess of translational energy is transformed mainly into translational energy of the products and perhaps internal energy of SCl; for H+PCl₃ the excess of translational energy allows the observation of the primary abstraction reaction, which could in earlier experiments at 300 K not be separated from secondary chemiluminescent processes. Bimodal rotational distributions were confirmed for several vibrational states of HCl formed in the systems $\text{H}$+Cl₂, and $\text{H}$+SCl₂. Bimodal rotational distributions were also detected in the chemiluminescent reaction H(0.04 eV)+CH₃SCl → HCl(v ? 5)+CH₃S.     

Syntheses and crystal structures of [Mg(HF)2](SbF6)2 and [Ca(HF)2](SbF6)2: new examples of HF acting as a ligand to metal centres

[Mg(HF)₂](SbF₆)₂ and [Ca(HF)₂](SbF₆)₂ monocrystals were grown from the corresponding hexafluoroantimonates(V) dissolved in anhydrous hydrogen fluoride. [Mg(HF)₂](SbF₆)₂ crystallizes in the space group Pnma (no. 62) with a=1249.1(4) pm, b=1230.2(4) pm, c=699.1(2) pm, V=1.0742(6) nm³, Z=4. Magnesium is octahedrally coordinated by six fluorine atoms from which two belong to two HF molecules. The structure can be represented by alternating rows of magnesium and antimony atoms running parallel to the c-axis. Magnesium atoms are connected by cis bridging Sb(2)F₆ units along the a-axis and by trans bridging Sb(1)F₆ units along the b-axis. In this way a three-dimensional network is formed.[Ca(HF)₂](SbF₆)₂ crystallizes in the space group P2₁/n (no. 14) with a=935.2(3) pm, b=1088.7(3) pm, c=1104.8(3) pm, β=106.697(5)°, V=1.0774(5) nm³, Z=4. The coordination sphere around the calcium atom consists of eight fluorine atoms which define the vertices of an Archimedean antiprism. The two HF molecules directly coordinate the calcium atom and their fluorine atoms are placed in the corners of different square faces of the Archimedean antiprism. The Ca-F(HF) distances are shorter than the Ca-F(Sb) distances. The Sb(1)F₆ and Sb(2)F₆ groups have four equatorial bridging fluorine atoms, while the Sb(3)F₆ groups have only two bridging trans F ligands. The Ca atoms in the [−1,0,1] plane are connected by equatorial F ligands of Sb(1)F₆ and Sb(2)F₆ units, forming a [Ca(SbF₆)⁺]_n layer. These layers are connected by trans bridging Sb(3)F₆ groups. HF molecules occupy the space between these layers and additionally contribute to the connection between the layers by hydrogen bonding.     

A DWBA study of angular distributions for the state-to-state reactive scattering process of F + H2 → HF + H

Based on our earlier three-dimensional DWBA theory, we discuss angular distributions and the roles of various angular momenta. The theory predicts a relatively small number of partial waves, backward scattering, and broadening of angular distributions with increased energy, for the reaction F+ H₂ (v_a = 0, j_a = 0) → HF (v_b = 2 j_b = 0) + H     

Distorted-wave calculations for the three dimensional chemical reaction H + H2(v ⩽ 2, j = 0) → H2(v′ ⩽ 2, j′, mj) + H

Calculations of the vibrational—rotational product state population distributions and differential cross sections for the chemical reaction H + H₂(v ? 2, j = 0) → H₂(v′ ? 2, j′, m_j) + H have been carried out on the Porter—Karplus potential energy surface. The vibrationally-adiabatic-distorted-wave (VADW) method has been used. The relative rotational product distributions, differential cross sections and the helicity m_j, dependences of these quantities for the v = 0 reaction agree well with accurate close-coupling results. The absolute integral cross sections are considerably smaller than the accurate quantum values, however. The calculations for the v = 1 reaction agree with the findings of previous sudden quantum, limited close-coupling and quasiclassical theoretical studies and experiments that product H₂(v′ = 1) is more likely to be produced than H₂(v′ = 0). For the reaction with v = 2, it is found that at high translational energies product H₂(v′ = 2) is favoured over H₂(v′ = 1) or H₂(v′ = 0). The VADW differential cross sections for the v = 1 and v = 2 reactions have a similar shape to those of the v = 0 reaction, with backward peaking when summed over all m_j states. The relative rotational distributions for the v = 2, j = 0 → v′ = 2, j and v = 1, j = 0 → v′ = 1, j reactions are also similar to those obtained for the v = 0, j = 0 → v′ = 0, j reaction, with low rotational excitation.     

Rotational and translation distributions of HF and NH3 subliming from solid NH4F

Infrared laser spectroscopy and time-of-flight mass spectrometry have been used to measure the rotational and translational distributions of HF and NH₃ subliming from a polycrystalline sample of NH₄F. The results of this study are compared with thermal desorption and gas-surface scattering experiments.     

Combined analysis of microwave and infrared spectra of methyl iodide: rotational and l-type doubling constants of the v5, v3+v6 and v2 states

The rotational constant B and the l-type doubling constant q were determined for the v₅, v₃+v₆ and v₂, states of CH₂I from the microwave transition frequencies, in combination with the infrared data previously reported. Since these vibrational states were coupled through the Fermi resonance and the xy-type E-E and A₁-E Coriolis resonances, the analysis was made by setting up and solving the complete form of the secular determinants of the energy matrices. The rotational and l-type doubling constants were determined as B₅, = 0.250 173 cm^?1, B₃₆ = 0.247 600 cm^?1, B₂ = 0.249 369 cm^?1, q₅ = ?0.000 027 cm^?1 and q₃₆ = ?0.000 179 cm^?1, which are unperturbed by Fermi and Coriolis interactions. Other band constants for v₅ and v₃+v₆ were also refined in accordance with the new values of B₅ and B₃₆. The present study indicated that the combined analysis of microwave and infrared spectral data was useful for the precise determination of vibration-rotation, levels in the perturbed system.     

Laser fluorescence studies of HF rotational relaxation

Rotation relaxation of HF in HF-Ar mixtures was observed using a laser infrared fluorescence technique. A specific vibrational-rotational state of HF was excited, and the fluorescence from HF was monitored. Total rotational energy-transfer rates, and individual state-to-state transition probabilities were obtained for υ = 1, J = 3 (ΔJ = ± 1, ±2) and υ = 1, J = 5; (ΔJ= ±1, ?2, ?3). The transition probabilities decreased with increasing ΔE_J,J, the energy transferred from R → T (rotation to translation). The data were fitted to a simple exponential model k_JJ, α exp(-ClΔE_J,J'l). C was estimated to be 1.55 ± 0.25 kcal^?1 mole.     

Vibrational Spectra of the Cyclic SN-Compounds S4N4, S4N4H4 and S3N3Cl3

The IR and Raman spectra of solid and dissolved S₄N₄, S₄N₄H₄, S₄N₄D₄ and S₃N₃Cl₃ have been recorded and are assigned according to D_2d, C_4v and C_3v symmetry respectively. In the solid state, many forbidden bands and splittings of degenerate vibrations are observed because of the symmetry lowering in the crystals. Due to the different size and shape of the rings and to strong coupling of the normal modes there is no clear correlation between the SN ring stretching vibrations and the strength of the SN bonds, except for the one of the E modes. However, the stretching force constant show the trend expected from changes in interatomic distances.     

Rotation-vibration-translation energy transfer in laser excited Li2 (B1Πu)

Using the method of laser fluorescence, inelastic collisions with rare gas atoms of electronically excited ⁷Li₂ molecules in the υ = 2 and 4 levels were studied. Vibrational transitions ranging from Δ = +2 to ?4 were observed. The simultaneous rotational transitions were completely resolved, and detailed rate constants k_{Δυ, ΔJ} for specific collision- induced quantum jumps Δυ, ΔJ were determined. The effect of secondary rotational relaxation was eliminated by an extrapolation to zero pressure. By integration over ΔJ, rate constants k_Δυ, were found. They are, within the error limits, independent of the collision partner and on the initial υ (2 or 4) and depend rather weakly on Δυ. These findings are compared with theoretical results from various methods, generally based on a collinear collision model. The apparent disagreement in all respects suggests strongly the importance of rotational degrees of freedom in the collision. Experimental evidence for this is the large amount of V — R transfer observed, which about equals the V — T transfer. The mean cross sections σ(Δυ) for specific vibrational transitions Δυ range between 6 and 15 A², among the largest ever observed.     

Photoacoustic study of vibration to translation-rotation transfer inch4 and cd4

The vibrational deactivation of CH₄ and CD₄ is studied experimentally in the gas phase using the photoacoustic method. Excitations of v₄ and v₃ modes are performed. The corresponding kinetic models are established using the fact that vibration-to-vibrati transfers are very efficient and hold the adjacent vibrational levels in a quasi-equilibrium distribution. The models are tested between 140 and 376 K and the vibration to translation-rotation rate constants are determined in pure CH₄ pure CD₄, and CH₄-CD₄ mixtures.     

Infrared spectra of KNaSO4 and K3Na(SO4)2

The infrared spectra, transmittance and polarized reflectance, of KNaSO₄ and K₃Na(SO₄)₂ are reported. Group theoretical analysis was carried out and a vibrational assignment proposed on basis of C_3v and D_3d symmetries. Factor group and site effects are discussed.     

Electric dipole moment of Ph3 in the v4 = 1 state

The electric dipole moment of PH₃ in the v₄ = 1 state was measured by means of the Stark effect on the first two l-type doubling transitions     

Structure des composes L4MS7 (L = La,Ce, Pr,Nd; M = Co,Ni) type K2NiF4 deforme

The structure of the compound La₄NiS₇ has been investigated by the X-ray method. The crystal, which is tetragonal with a = 4.0801 Å and c = 16.334 Å, space group $\text{I}{}_4\text{mmm}$, exhibits superstructure reflections with a′ = 4a, c′ = c, and v′ = 16 v. The structure has been solved with substructure reflections (R = 0.056), the complementary structure reflections being too weak for measurement. This structure is a distorted K₂NiF₄ type. Lanthanum atoms are in 7–8-fold coordinated sites, one nickel atom is in a distorted octahedral site, and the other nickel atom in a site with coordinance 7.     

Laser-induced fluorescence in N2 and N+2 by multiple-photon excitation at 266 nm

The fluorescence transitions corresponding to the second positive system of N₂ (C³Π_u → B³Π_g) for Δv = 0, 1 and the first negative system of N⁺₂(B²Σ⁺_u → X²Σ⁺_g) for Δv = 0, 1, 2 have been observed following laser-induced mul excitation of N₂.     

Vibrational relaxation of CO2(v3) by O atoms

The vibrational relaxation time for CO₂(v₃) + O(³P) has been measured by laser fluorescence. The observed value, βCO₂.O = 0.21 ± 0.04 μsec, is an order of magnitude lower than the relaxation time for self-collisions.     

Vibration excitation of no in its collisional quenching of O2 (1▵g)

Infrared emission of NO from levels up to v = 4 is observed in its gas phase quenching of O₂(¹ ?_g). The predominance of population of the highest accessible level of NO (v = 4) is due to matching of energies.     

Synthesis, vibrational and NMR spectroscopic characterization of [N(CH3)4][IO2F2] and X-ray crystal structure of [N(CH3)4]2[IO2F2][HF2]

The salt, [N(CH₃)₄][IO₂F₂], was prepared from [N(CH₃)₄][IO₃] and 49% aqueous HF, and characterized by Raman, infrared, and ¹⁹F NMR spectroscopy. Crystals of [N(CH₃)₄]₂[IO₂F₂][HF₂] were obtained by reduction of [N(CH₃)₄][cis-IO₂F₄] in the presence of [N(CH₃)₄][F] in CH₃CN solvent and were characterized by Raman spectroscopy and single-crystal X-ray diffraction: C2/m, a = 14.6765(2) Å, b = 8.60490(10) Å, c = 13.9572(2) Å, β = 120.2040(10)°, V = 1523.35(3) Å³, Z = 4 and R = 0.0192 at 210 K. The crystal structure consists of two IO₂⁻F₂ anions that are symmetrically bridged by two H⁻F₂ anions, forming a [F₂O₂I(FHF)₂IO₂F₂]⁴⁻ dimer. The symmetric bridging coordination for the H⁻F₂ anion in this structure represents a new bonding modality for the bifluoride anion.     

The crystal structure of Ca3Cu3(PO4)4

Single crystals of Ca₃Cu₃(PO₄)₄ synthesized hydrothermally at 420°C and 55 kpsi (3.8 kbar) were found to occur in the space group $\text{P2}{}_1\text{a}$ (No. 14) with a = = 17.619(2), b = 4.8995(4), c = 8.917(1)Å, β = 124.08(1)°, and Z = 2. Full-matrix least-squares refinement of the structure using diffractometer data converged to a final anisotropic R = 0.037 (R_w = 0.046). The two calcium atoms are in six- and nine-coordination and the two copper-containing polyhedra (four- and five-coordinated) are similar to those previously found in Cu₃(PO₄)₂.     

Assignment of the microwave spectrum of trioxane in the v19(E) = v20E) = 1 state

An analysis of the rotational spectrum associated with two degenerate states simultaneously excited by one quantum is carried out for the first time for symmetric top molecules. The microwave spectrum of trioxane in the v₁₉(E) = v₂₀(E) = 1 state has been measured in the range 60–145 GHz and assigned using a graphical method. Accurate molecular parameters are determined by diagonalization of the energy matrices obtained by factoring the matrix constructed using the eigenvectors of the zeroth-order Hamiltonian as a basis.     

The υ3 = 1 state of 37ClO2 studied by laser-microwave double resonance

Laser-microwave double-resonance experiments have been carried out which enable rotational and coupling constants of the υ₃ = 1 state of ³⁷ClO₂ to be determined. This work utilized an accidental coincidence between the 9R(24)C¹⁸O₂ laser line and hyperfine components of the ^QR_o(1) transition of the v₃ band of ³⁷ClO₂. A novel type of IR-MW-MW triple resonance is described.