Emission and excitation spectra of the CCN free radical in solid argon

We demonstrate that 1216 Å photolysis of acetonitrile in rare gas solids leads to efficient production of the CCN free radicals. These radicals emit in solid Ar with a 170 ns lifetime. Study of the A²Δ_i → X²Π_i emission spectra provides values of 1066 and 1717 cm^?1, respectively, for the ground state stretching frequencies. Several weaker vibronic bands are interpreted in terms of the bending fundamentals ν′₂ and ν″₂.     

High-lying <Superscript>1</Superscript>P° doubly-excited states of H<Superscript>-</Superscript> and He below the N = 3–13 hydrogenic thresholds

An experimental study of the long range behavior of the ground state X¹Σ⁺ _g of Sr₂ is performed by high resolution spectroscopy of asymptotic vibrational levels and the use of available photoassociation data. Ground state levels as high as v’’=60 (outer turning point at 23 Å and 0.1 cm^-1 below the asymptote) could be observed by Fourier-transform spectroscopy of fluorescence progressions induced by single frequency laser excitation of the v’=4, J’=9 rovibrational level of the state 2¹Σ⁺ _u. A precise value of the scattering length for the isotopologue ⁸⁸Sr₂ is derived and transferred to all other isotopic combinations by mass scaling with the given potential. The derived potential together with already published information about the state 2¹Σ⁺ _u directs to promising optical paths for producing cold molecules in the electronic ground state from an ultracold ensemble of Sr atoms.     

气相CCl2自由基的发射光谱

在CCl₄蒸汽的直流放电中,观测了从520到630nm波长范围的荧光发射并确认为CCl₂自由基A→X跃迁。近400条谱带归属为³⁵Cl-C-³⁵Cl和³⁵Cl-C-³⁷Cl的(v₁′,v₂′,0)→(v₁″,v₂″,0)一系列前进带组,并排列成Deslandres表。光谱分析给出CCl₂在激发态和基态的v₁和v₂振动频率及同位素位移,其中气相CCl₂在基态的数据尚未见文献报道。 关键词：     

Fluorescence from the 2B1 state of NO2 excited at 4545 Å

The 4545 Å line of the Ar⁺ laser has been used to excite a ^pR₁ line of a vibrational band of the ²B₁-²A₁ system of nitrogen dioxide. Fluorescence from the upper level to the ground electronic state forms a long progression in the bending vibration. This progression can be followed from v″₂ = 0 up to v″₂ = 12, and the fluorescence intensity passes through several local minima as a function of v″₂. The main features of the intensity distribution can be reproduced using a model Hamiltonian which separates the bending and rotation from the stretching vibrations. This Hamiltonian can also be used to reproduce the fluorescence frequencies by adjusting the potential function of the lower state.     

Matrix-isolation study of the vacuum-ultraviolet photolysis of NF3: The electronic spectrum of the NF2 free radical

The vacuum-ultraviolet photolysis of NF₃ in an argon or a carbon monoxide matrix at 14°K leads to the production of NF₂, identified by its infrared absorption. F-atom photodetachment also leads to the appearance of FCO in the carbon monoxide matrix studies. The photodissociation of NF₂ by 2537 Å radiation has been confirmed. The appearance of a band system near 2600 Å with position and band spacings close to those previously reported for NF₂ in the gas phase demonstrates that the lower state of the gas-phase transition is the ground state of the molecule and confirms the assignment of the observed structure to a progression in the upper-state bending vibration.     

Laser excited fluorescence spectrum of nitrogen dioxide

The fluorescence spectrum of NO₂ excited by a single mode argon-ion laser was studied at a spectral resolution of 0.1 cm^?1. In particular the Stokes and the anti-Stokes ν₂ band excited by the 5145 Å line of an argon-ion laser were examined in detail. Some of the vibrational and rotational parameters of the ground electronic state and the rotational constants of the B₂ vibronic state were obtained.     

Ultraviolet laser-induced fluorescence spectrum of fluorochlorocarbene in solid argon

CFCl has been produced for spectral investigation by matrix reactions of alkali metal atomic beams with CFCl₃ in argon followed by rapid quenching to 15°K on a tilted copper wedge. When these samples were irradiated with near uv light from a krypton ion laser, a very intense, highly structured fluorescence spectrum was observed. This emission system extended from about 25 000 cm^?1 to 15 000 cm^?1 and peaked in intensity at about 22 000 cm^?1. The three most intense progressions are assigned to transitions from a common excited state to ground state levels (0v₂0), (1v₂0) and (1v₂1). New molecular constants determined from these progressions include $\text{ω}{}_2{}^0\text{= 446}\text{cm}{}^{\mathrm{?1}}$, x₂₂ = ?1.2 cm^?1, x₁₂ = ?3 cm^?1, x₂₃ = ?4 cm^?1, and x₁₃ = ?6 cm^?1. CFCl was also produced by in situ photolysis of CFCl₃ using laser plasma emission and by alkali metal atom reactions with CF₂Cl₂, CF₂ClBr, and CHFCl₂.     

Laser characteristics of KCL:O-2

Amplified spontaneous emission and laser action have been observed at 77 K in KCL crystals containing the superoxide ion (O^-₂). The laser operates in two bands of width ～50 Å centered at 6350 Å and 5984 Å. These bands are the (lattice) phonon sidebands of vibronic transitions of the superoxide ion. At lower temperatures (～6 K) amplified spontaneous emission is observed in the zero phonon line at 6294 Å.     

Raman spectroscopic study of the uranyl selenite mineral marthozite Cu[(UO2)3(SeO3)2O2]·8H2O

The mineral marthozite, a uranyl selenite, has been characterised by Raman spectroscopy at 298 K. The bands at 812 and 797 cm⁻¹ were assigned to the symmetric stretching modes of the (UO₂)²⁺ and (SeO₃)²⁻ units, respectively. These values gave the calculated U O bond lengths in uranyl of 1.799 and/or 1.814 Å. Average U O bond length in uranyl is 1.795 Å, inferred from the X‐ray single crystal structure analysis of marthozite by Cooper and Hawthorne. The broad band at 869 cm⁻¹ was assigned to the ν₃ antisymmetric stretching mode of the (UO₂)²⁺ (calculated U O bond length 1.808 Å). The band at 739 cm⁻¹ was attributed to the ν₃ antisymmetric stretching vibration of the (SeO₃)²⁻ units. The ν₄ and the ν₂ vibrational modes of the (SeO₃)²⁻ units were observed at 424 and 473 cm⁻¹. Bands observed at 257, and 199 and 139 cm⁻¹ were assigned to OUO bending vibrations and lattice vibrations, respectively. O H···O hydrogen bond lengths were inferred using Libowiztky's empirical relation. The infrared spectrum of marthozite was studied for complementation. Copyright © 2008 John Wiley & Sons, Ltd.     

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.     

Investigation of the luminescence spectrum of UO2MoO4

By time-resolved spectroscopy the intrinsic emission spectrum of UO₂MoO₄ at 4.2 K is obtained. The main progressions in the vibronic structure are identified as couplings with the A_g correlation field components of the symmetric and asymmetric UO₂ stretching modes. The intrinsic zero-phonon line in the emission and excitation spectrum is shown to be split both by the crystal field and correlation field. The steady-state emission spectrum at 4.2 K is dominated by emission from traps. The vibronic structure of the trap emission reveals that all traps are distorted uranyl groups.     

The structure of the triethylenediamine molecule in an excited electronic state

Ultraviolet absorption spectrum has been observed of triethylenediamine (1,4 diazabicyclo[2.2.2]octane) ($\text{D}{}_{\mathrm{<mtext>3</mtext><mtext>A</mtext><mtext>?</mtext>}}$) vapor in the 2200–2600 Å region, and an analysis has been made of its vibrational structure. The vibronic 0-0 transition was determined to be at 2513.65 Å (39782.8 cm^?1), and in the 2540–2590 Å region there were four hot bands found: two from the a₁′-type vibrational levels and two from the a₂″-type vibrational levels of the ground electronic state. The fine structures of these hot bands were examined with 0.49 Å/mm dispersion (slit width = 50 μm). For each of the two a₂″-type hot bands, a progression with 30 ～ 40 cm^?1 spacings was observed; whereas, no such progressions were found for the a₁′-type hot bands, in which absorption peaks are much more concentrated within narrow ranges. These progressions were attributed to a large-amplitude twisting motion of triethylene-diamine molecule. For explaining the whole energy-level structure, another large-amplitude motion, has been postulated. That is a double-minimum deformation motion along the molecular axis; in each minimum, one of the two NC₃ umbrellas is half-way open and the other NC₃ umbrella is half-way closed. The height of the potential barrier between these two minima has been estimated to be 1586 cm^?1.     

Resonance fluorescence spectrum of nitrogen dioxide

We report an investigation of the resonance fluorescence spectrum of NO₂ excited by several laser lines. Sixty transitions, mostly in ν₂ progressions of the ground state, have been assigned. Analysis of the spectra extend the knowledge of the ground state constants, especially of the anharmonic coefficients. It is possible to establish that transitions are occurring to a ²B₁ state and to a ²B₂ state in the same energy region.     

Energy transfer in I2-HD mixtures

Collisional energy transfer from the vibrational level ν=43 of the B state of I₂ in I₂-HD mixtures was investigated by exciting with the 5145 Å line of an Ar⁺ laser. Relaxation rates were measured for different vibrational quantum changes in state B. Analysis of the energy transfer data indicated the possibility of a resonant energy transfer mechanism taking place between the excited I₂ molecules and the ground state HD molecules (vibrational to rotational relaxation).     

Non-adiabatic transition in C2H5OH+ on a light-dressed potential energy surface by ultrashort pump-and-probe laser pulses

We experimentally investigate how parameters of ultrashort laser pulses such as the pulse width and wavelength could induce changes in the dynamics of vibrational wave packets on the light-dressed-potential energy surface (LD-PES) of C₂H₅OH⁺ using a pump-and-probe pulse excitation scheme. The probability of non-adiabatic transition at 800 nm from the singly ionized ground state to the repulsive excited state leading to C–O bond breaking is enhanced when a probe laser pulse is delayed by ～180 fs. At this pulse delay, on the other hand, C–C bond breaking is significantly suppressed. Therefore, the deformation of LD-PES is considered to change the direction of the wave packet traveling originally along the C–C stretching into the direction along the C–O stretching. This non-adiabatic transition leading to the redirection of the dissociating wave packet is found to occur more efficiently at the probe laser wavelengths at 400 nm than at 800 nm. The critical pulse delay is still ～180 fs even at 400 nm.     

Hot band spectroscopy of DCBr near 0.96 μm

High resolution measurements of the 2⁰ ₂ (bending) hot band of the ùA′ band system of deuterobromomethylene between 10 290cm^?1 and 10 540cm^?1 are described. The spectra were recorded by direct absorption of a continuous-wave frequency-modulated external cavity diode laser following pulsed ultraviolet laser photolysis of deuterated bromoform. Although the bending vibrational spacings in the ùA′ state are not regular, the rotational structure in its (020) level was found to be unperturbed at the accuracy of the experimental measurements. This observation provides strong evidence that the position of the excited triplet ó A″, state lies to higher energy, at least 1637cm^?1 above the zero point level of the ground state.     

Raman spectroscopy of hydrogen‐arsenate group (AsO3OH) in solid‐state compounds: copper mineral phase geminite Cu(AsO3OH)·H2O from different geological environments

The participation of hydrogen‐arsenate group (AsO₃OH)²⁻ in solid‐state compounds may serve as a model example for explaining and clarifying the behaviour of As and other elements during weathering processes in natural environment. The mineral geminite, a hydrated hydrogen‐arsenate mineral of ideal formula Cu(AsO₃OH)·H₂O, has been studied by Raman and infrared spectroscopies. Two samples of geminite of different origin were investigated and the spectra proved quite similar. In the Raman spectra of geminite, six bands are observed at 741, 812, 836, 851, 859 and 885 cm⁻¹ (Salsigne, France), and 743, 813, 843, 853, 871 and 885 cm⁻¹ (Jáchymov, Czech Republic). The band at 851/853 cm⁻¹ is assigned to the ν₁ (AsO₃OH)²⁻ symmetric stretching mode; the other bands are assigned to the ν₃ (AsO₃OH)²⁻ split triply degenerate antisymmetric stretching mode. Raman bands at 309, 333, 345 and 364/310, 333 and 345 cm⁻¹ are attributed to the ν₂ (AsO₃OH)²⁻ bending mode, and a set of higher wavenumber bands (in the range 400–500 cm⁻¹) is assigned to the ν₄ (AsO₃OH)²⁻ split triply degenerate bending mode. A very complex set of overlapping bands is observed in both the Raman and infrared spectra. Raman bands are observed at 2289, 2433, 2737, 2855, 3235, 3377, 3449 and 3521/2288, 2438, 2814, 3152, 3314, 3448 and 3521 cm⁻¹. Two Raman bands at 2289 and 2433/2288 and 2438 cm⁻¹ are ascribed to the strong hydrogen bonded water molecules. The Raman bands at 3235, 3305 and 3377/3152 and 3314 cm⁻¹ may be assigned to the ν OH stretching vibrations of water molecules. Two bands at 3449 and 3521/3448 and 3521 cm⁻¹ are assigned to the OH stretching vibrations of the (AsO₃OH)²⁻ units. The lengths of the O H···O hydrogen bonds vary in the range 2.60–2.94 Å (Raman) and 2.61–3.07 Å (infrared). Two Raman and infrared bands in the region of the bending vibrations of the water molecules prove that structurally non‐equivalent water molecules are present in the crystal structure of geminite. Copyright © 2009 John Wiley & Sons, Ltd.     

Concentration effects on absolute depolarized Rayleigh ratios and effective polarizability derivatives of CS2 in liquid mixtures with CCl4

Experimental results are reported from polarized and depolarized Raman intensity measurements in combination with absolute depolarized Rayleigh ratios of liquid CS₂ in CCl₄ mixtures at 25°C. Using a calibrated Raman spectrometer it was possible to determine the concentration dependence of g ₂ · γ² _eff of CS₂. Intensity measurements of the polarized and depolarized Raman spectra of the symmetric stretching vibration of CS₂ under the same conditions allowed the determination of the effective values of α₀₁ and γ₀₁ respectively to the normal mode Σ⁺ _g in the liquid phase. In the neat liquid, α₀₁ = 0·19 ų and γ₀₁ = 0·22 ų. In mixtures with CCl₄ the values of α₀₁ decrease at lower CS₂ concentration whereas the values of γ₀₁ increase. These results indicate that the isotropic induced dipole field is increasingly cancelled as the environment becomes more isotropic while the anisotropic part is amplified in CCl₄. A report is also given of an anomalous concentration behaviour of the intensity of the combination mode v ₁ + v ₂-v ₂ on the low frequency side of the v ₁ transition which is amplified relative to the intensity of the v ₁ mode as the CCl₄ concentration increases.     

Fourier Transform and Intracavity Laser Spectroscopy of NiCl System H: Identification of a [12.3] Σ State

The (0,0) vibronic band of NiCl system H near 12 259 cm⁻¹ was recorded at high resolution in absorption using intracavity laser spectroscopy (ILS) and in emission by Fourier transform (FT) spectroscopy. Though it was originally assigned in 1962 as the (1,1) vibronic band of ²Π_3/2-X²Δ_5/2, we have shown that this transition is the (0,0) vibronic band associated with a newly identified ²Σ⁺ excited state and the X²Π_3/2 ground state. The molecular constants for the new ²Σ⁺ electronic state were derived from the rotational analysis. For the ILS absorption spectra, the NiCl molecules were produced in a nickel hollow cathode, operated with a small amount of CCl₄. Line positions were referenced to iodine spectra observed from a heated extracavity cell using the intracavity laser as the light source. For the FT spectra, excited NiCl molecules were produced in a King-type carbon tube furnace.     

The Rotational Analysis of the Five new Vibronic Bands of No2 in the Range 5050-5200 Å

The five new vibrational bands in the range 5050-5200 Å of the laser induced fluorescence excitation spectra of NO₂ were measured and rotationally assigned at room temperature. Though the spectra were rather congested, we can determine the band origins, and rotational and spin-rotation constants for these bands. All rotational structures analyzed are of the parallel type. It was shown that the electronic excited state òB₂ were heavily perturbed by the high lying vibration levels of ground state [Xtilde] ² A ₁ and that the interactions between these two electronic states was the main rationale for the complexity of NO₂ visible spectra.