2P12 excited iodine formation in the F + HI reaction

Fluorine atoms produced in a microwave discharge of SF₆ were mixed with HI molecules in a flow system. Groundstate and excited iodine atoms were monitored by measuring the absorption of atomic emission lines from an iodine resonance lamp. A model taking into account the formation of excited iodine atoms through the reactive channel as well as the VE energy transfer process from vibrationally excited HF molecules is discussed. The fraction of excited iodine atoms formed in the reaction is shown to be 0.5.     

Studies of the reactions of Br(2P32) and Br(2P12) atoms with CH3F

The photobromination of methyl fluoride at low pressures has been studied experimentally. Bromine atoms in the ground (²P_{$\text{3}\text{2}$}) and excit     

Wavelength dependence of the I(52P12,32) branching ratio from ICN Ã state photolysis

Quantum yields for the production of I(5²P$\text{1}\text{2}$) atoms from the photolysis of ICN in the à state continuum are presented as a function of wavelength. Evidence is presented for the existence of at least three electronic states giving rise to the absorption spectra. Primary photophysical processes involved in the dissociation of ICN are discussed.     

Electronic-to-vibrational energy transfer from Br (42P12 to HF

Room temperature experiments have measured the rate of electronic-to-vibrational energy transfer between spin—orbit excited Br(4²P_{$\text{1}\text{2}$}) and HF. The Br^* + HF quenching rate is very fast, (1.1 ± 0.2) × 10⁶ s^?1 torr^?1, due to a near resonance between the spin—orbit splitting and the vibrational spacing. The majority of the Br^* spin—orbit energy goes directly into HF vibration.     

Collisional deactivation of laser-excited Br*(2P12) atoms with halogen and interhalogen molecules

Deactivation rates of spin-orbit excited Br*(²P_{$\text{1}\text{2}$}) atoms by halogens I₂, Br₂, and Cl₂ and interhalogens IBr, ICl and BrCl have been measured by laser-excited, time-resolved infrared emission techniques. The results are effectively explained in terms of a collision complex formation model.     

Efficient production of I(52P12) in the photodissociation of ICN

Photolysis of ICN in the A ← X continuum near 260 nm is shown to produce electronically excited iodine atoms with a quantum yield of 0.5 ± 0.1. In conjunction with previous photofragment spectroscopy and laser induced fluorescence studies, this result suggests that at least two excited states of ICN play a role in the photodissociation of this molecule.     

Kinetic spectroscopy in the far vacuum ultraviolet. Part I: Detection of (2p5) 2P32,12 fluorine atoms using atomic resonance spectrometry in the wavelength range 95–98 nm

A new experimental system for atomic resonance spectrometry at λ < 105 nm in a discharge-flow system is described. The spectrum of a fluorine resonance lamp has been studied, and possible precursors for the 2p⁴ 3s excited F atoms formed are suggested. Ground state (2p⁵²P_{$\text{3}\text{2}$}) and J-excited ²P_{$\text{1}\text{2}$} F atoms have been detected for the first time in resonance absorption and fluorescence using the first resonance transitions with wavelengths between 95.2 and 97.8 nm. Preliminary measurements (using both ⁴P-²P and ²P-²P lines) of the variations with concentration of absorption intensity by ground state F ²P_{$\text{3}\text{2}$} and by J-excited F ²P_{$\text{1}\text{2}$} atoms are reported; F atom concentrations were measured using a titration method based on the rapid reaction, F + Cl₂ → FCl + Cl.     

Laser induced photodissociation of C2F5I. Radiative lifetime of the metastable iodine atom (2P12)

Excited iodine atoms I(²P_{$\text{1}\text{2}$}) are formed by laser irradiation of C₂F₅I at 2950 Å. The mean radiative lifetime τ of these metastable atoms and their bimolecular rate constant k₂ for deactivation in collissions with C₂F₅I were measured to be: τ = 108 ± 10 ms; k₂ = (1.8 ± 0.1) × 10^?17 cm³/molec s.     

Evidence for predissociation of Rb*2(C 1Πu) into Rb*(2P12) and Rb(2S12)

A nozzle beam of rubidium is irradiated by the 4765 A line of the argon ion laser, and the resulting fluorescence is spectroscopically analyzed. Under these collision-free conditions, the emission consists of molecular fluorescence from the Rb₂ C ¹Π - X ¹Σ⁺_g electronic system as well as atomic fluorescence from the Rb ²P_{$\text{3}\text{2}$} fine structure component (the Rb D₂ line) only. The latter transition is caused by partial predissociation (? 25%) of the Rb₂ C ¹Π_u state. Within experimental error, the atomic fluorescence is not polarized and its intensity does not change when an electric field of 14.7 kV/cm is applied across the excitation region. The molecular fluorescence is polarized and has the value P = 0.345 ± 0.0009. This is interpreted to be caused by the superposition of P and R as well as Q lines. Although it is not possible to identify which state causes the predissociation of the Rb₂ C ¹Π_u state, arguments are presented that only the Rb D₂ line would appear provided the predissociation is an adiabatic process.     

Large isotope effect in the quenching of I(52P12) by benzene and benzene-d6

Spin—orbit relaxation of I(5²P_{$\text{1}\text{2}$})(ΔE = 0.94 eV) by benzene-d₆, has been studied at 297 K, using time-resolved atomic resonance fluorescence. A large isotope effect is observed, k_C6H6 = (4.6 ± 0.7) × 10^?13 cm³ molecule^?1 s^?1, and k_C6D6 = (9.9 ± 1.0) × 10^?15 cm³ molecule^?1 s^?1, despite evidence that formation of a bound collision complex may contribute to the quenching mechanism. The roles of resonant energy transfer channels, Franck—Condon factors and the density of final states, in the quenching process, are discussed.     

Heat capacity and thermodynamic properties of ramsdellite,Li2Ti3O7, and spinel,Li43Ti53O4

The heat capacity and heat content Li_{$\text{4}\text{3}$}Ti_{$\text{5}\text{3}$}O₄ and Li₂Ti₃O₇ have been measured in the temperature range 198—960 K. The lattice and dilation contributions to the heat capacity have been estimated. The standard thermodynamic functions and the high temperature enthalpy and entropy have been derived. The lattice heat capacity of Li_{$\text{4}\text{3}$}Ti_{$\text{5}\text{3}$}O₄ spinel appears to be consistent with the phonon model put forward by Grimes.     

Emission spectra of the noble-gas halides: the B12A12 system

The B$\text{1}\text{2}$—A$\text{1}\text{2}$ transition has been detected in the emission spectra of ArBr, KrBr, Krl and XeI at low pressure. Comparison with the well-known /ldB–X” continua implies that, in many cases, the latter is heavily overlapped by C$\text{3}\text{2}$—A$\text{3}\text{2}$ emission.     

Tunable laser photodissociation: quantum yield of I★(2P12) from Ch2I2

Tunable laser I^★(²P_{$\text{1}\text{2}$}) quantum-yield measurements are presented for CH₂I₂ in the wavelength range 248–340 nm. The results suggest that a curve-crossing mechanism is operative in the dissociation.     

Yield of I(2Psol:12) in the photodissociation of CH2I2

The production of I(²P_{$\text{1}\text{2}$}) in the photolysis of CH₂I₂ has been studied optoacoustically at excitation wavelengths between 365.5 and 247.5 nm. Bands found at 32200 and 47000 cm^?1 correlate with I(²P_{$\text{3}\text{2}$}) whilst those at 34700 and 40100 cm^?1, which correlate with I(²P_{$\text{1}\text{2}$}), give final ²P_{$\text{3}\text{2}$}/²P_{$\text{1}\text{2}$} ratios of 1.75 and 1.1, respectively, after curve crossing.     

Far-infrared laser magnetic resonance spectrum of SeD (X2Π32)

Far-infrared laser magnetic resonance (LMR) spectra of SeD have been detected at 513 μm using a formic acid laser, and assigned to Zeeman components of the J = $\text{3}\text{2}$ → $\text{5}\text{2}$ transition in the six isotopic forms ^{82,80,78,77,76,74}SeD. Analysis yields the following B_o constants (cm^?1): ⁸²SeD 3.96047, ⁸⁰SeD 3.96284, ⁷⁸SeD 3.96532, ⁷⁷SeD 3.96657, ⁷⁶SeD 3.96793 and ⁷⁴SeD 3.97066. These values, combined with B_o for ⁸⁰SeH from 5.6μm LMR, yield r_e = 0.14634 nm for SeD.     

The lattice vibrations of cubic A12MIVF6 compounds

The luminescence spectra of Cs₂MnF₆ and of Mn⁴⁺ in Cs₂GeF₆, Cs₂SiF₆ and Rb₂SiF₆ show bands due to low frequency vibrations which are not assignable using the unit cell model. Comparison of these spectra with infrared and Raman spectra and with a model for the lattice dynamics has suggested probable assignments for the vibrational and luminescence spectra.     

NMR dipolar echoes in solids containing spin-12 pairs

A model of loosely-coupled spin-$\text{1}\text{2}$ pairs is used to explain the proton NMR dipolar echo behaviour observed in crystalline hydrates. This behaviour is distinctly different from that previously predicted and observed in solids containing single spin-$\text{1}\text{2}$ nuclei and is shown to originate in the differentiation of the intrapair from the interpair dipolar interactions.     

Vibronic-coupling and spin relaxation in discrete spin-12 transition-metal complexes

Solvent electric field fluctuations combined with vibronic coupling can account for the observed field- and temperature-insensitive NMR decay rates (T^?1_1N) in transition-metal complexes whose formal ground state is orbitally degenerate.     

T−12-law of dc conductivity 1N Langmuir films

Measurements of dc conductivity of Cd-stearate multilayer films below room tenperature down to liquid nitrogen temperature have revealed the temperature dependence σ = σ₀ exp(?AT^{?$\text{1}\text{2}$}). This relation, together with the values of σ₀ and A, confirms the theoretical predictions for hopping conduction in a multilayer system associated with interface states.     

Exact analytic solution of the spin 32 combined Zeeman-quadrupole Hamiltonian

The secular equation arising from the combined spin $\text{3}\text{2}$ Zeeman-quadrupole Hamiltonian has recently been solved in analytic form (refs. 1,2). Energy level and frequency expression, valid for all magnetic field strengths, are derived in a form highly suitable for analysis of resonance patterns arising from rotation of a single crystal about an axis perpendicular to the magnetic field direction. Theoretical rotation patterns are presented for the six possible transitions. A simple method for measurement of the quadrupole parameters is discussed.