Analysis of the D1 Δ—X1Σ+ transition in CO observed by two-photon excitation

The D¹ Δ—X¹Σ⁺ transition in carbon monoxide has been observed by two-photon excitation with a frequency-doubled pulsed dye laser. The rotational structure of thirteen υ′= 0 bands has been analyzed: the υ′= 6–12 bands in ¹²C¹⁶O, υ′= 7, 10 and 12 in ¹³C¹⁶O, and υ′= 7, 10 and 12 in ¹³C¹⁸O. Detailed assignments are presented, and from them the rotational and vibrational constants of the D¹ Δ state have been determined. Using a single mass-reduced fit, molecular constants are calculated for all three isotopomers. Analysis of the 7-0 band of the I¹Σ⁻−X¹Σ⁺ transition is also given.     

Millimeter spectrum of carbon monosulfide rare isotopes

The millimeter spectra of carbon monosulfide rare isotopic species in natural abundance have been observed inside a radiofrequency plasma. Molecular constants have been derived for the v=0 ground state of ¹²C³⁶S, ¹³C³⁴S and ¹³C³³S, and for v = 0 and v = 1 states of ¹²C³³S.     

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.     

Fourier transform spectra of carbon disulfide in the 2800–3000 cm−1 region

Fourier transform spectra were recorded for carbon disulfide in the region between 2800 and 3000 cm⁻¹. A total of 20 bands for the carbon disulfide isotopologue ¹²C³²S₂, 2 for ¹²C³²S³³S, 8 for ¹²C³²S³⁴S, 1 for ¹²C³⁴S₂ and 5 for ¹³C³²S₂ have been investigated. Two bands 13¹1–01¹0 of ¹²C³²S₂ and 12⁰1–00⁰0 of ¹²C³²S³⁴S present local perturbations.Vibrational frequencies and rotational constants have been determined for the bands.     

Resonance in the rotational dependence of the isotope-selective reaction between IiCl(A 3Π1) and acetylene

The rotational dependence of the isotope selective reaction between IⁱCl(A ³Π_l, υ′, J′) and acetylene (C₂H₂, C₂D₂) forming the photoaddition product 1,2-iodo-chloro-ethyene was studied for ν′ = 19 and ν′ = 20. The enrichment factor in the photoproduct shows resonances for J′ = 32, ν′ = 19 and J′ = 6, υ′ = 20.     

Dynamic aspects of the reaction O(1D) + H2S → OH + SH

The energy distribution of nascent OH(²Π, υ, J) produced in the reaction of O(¹D) with H₂S has been measured by laser-induced fluorescence. The rotational distributions in υ″ = 0 and υ″ = 1 are Boltzmannian with temperature parameters T_r″-0 = 2300 ± 100 K and T_r⁻-1 = 2650 ± 150 K. A population ratio N(υ″ = 1)/N(υ″ = 0) = 0.17 is observed. The product-state distribution over the different spin and A components is statistically within the experimental uncertainty of 20%. A comparison of the OH product populations from the title reaction with the well known OH yield from the O(¹D)+H₂O reaction shows that 25% of the reactive encounters follow the reaction channel which produces OH in υ″ = 0 and υ″ = 1.     

Interpretation of the microwave spectrum of 2-methoxy ethylamine using its ab initio structures

The 7₃ ← 6₃ μ_aK₋₁ doublet line series of 2-methoxy ethylamine, previously recorded with the radiofrequency microwave double resonance technique, was interpreted for the T and G conformations of this compound with a number of structural models including the 4-21G optimized geometries. A single model of G can reproduce the doublet series as the vibrational progression of the CO skeletal mode, starting with the υ_CO = 0 groundstate at 35 457 MHz, and stepping in approximately 95 MHz intervals up to the vibrational satellite of υ_CO = 9, with the υ_CO = 5 doublet missing. When model calculations are performed for T with the structural parameters of G which reproduce the 7₃ ← 6₃K₋₁ doublet series, except for rotating the NH₂ group by 120° to obtain T, the frequency of its groundstate doublet is found at lower frequencies than that of G. In contrast to this, when the empirically corrected 4-21G parameters of T are used in the analysis, the calculated groundstate of T coincides with the expected υ_CO = 6 doublet of G. The 4-21G geometries of G and T are in good agreement with the rotational constants and the conformational energy difference derived from the microwave spectra. Thus, this analysis clearly confirms the assignment of the observed 7₃ ← 6₃K₋₁ series as the progressions of the υ_CO = 0 to υ_CO = 4 states of G, and the υ_CO = 0 to υ_CO = 3 states of T.     

The microwave spectrum,structure and centrifugal distortion constants of 2-chloroacrylonitrile

The microwave spectrum of 2-chloroacrylonitrile has been studied in the 26.5–40 GHz region. A total of 99 a- and b-type rotational transitions have been measured and assigned for CH₂ =C³⁵Cl(CN),yielding values for the rotational constants (in MHz): A = 6973.27, B = 3148.16, C = 2165.95. For CH₂=C³⁷Cl(CN) a total of 53 transitions have been measured and assigned and the rotational constants obtained are (in MHz): A = 6909.35, B = 3081.17, C = 2127.98. The distortion effects have also been studied and the quartic distortion constants have been evaluated. From the observed hyperfine structure, the chlorine nuclear quadrupole coupling constants have been obtained. The structure of vinyl cyanide and vinyl chloride can be transferred to account remarkably well for the observed rotational constants.     

Characterisation by rotational spectroscopy of a hydrogen-bonded dimer formed between H2O and HCN

The rotational spectra in the vibrational ground states of (H₂O, HC¹⁴N) and (H₂O, HC¹⁵N) have been assigned in the frequency range 6–19 GHz. Values of rotational constants (B_O, C_O) and centrifugal distortion constants (Δ_J, Δ_JK) have been determined for both species, while the ¹⁴N-nuclear quadrupole coupling constants x_aa and x_bb have been established for the first. Observations concerning additional hyperfine structure arising from H,H nuclear spin-nuclear spin coupling in the H₂O subunit suggest that (H₂O,HCN) has a pair of equivalent protons and is effectively planar in the zero-point state. Observed spectroscopic constants are consistent only with the arrangement H₂O…HCN, with r(O…C) = 3.1387 Å.     

Chemiluminescent emissions from the gas phase reactions of ozone with acetylene and allene

Chemiluminescence spectra (300–800 nm) from the reactions of ozone with acetylene and allene have been obtained. These spectra show the production of electronically excited CHO, OH(²Π_i, υ ? 9) and possibly C₂(B³Π_g, υ′ = 0 → X³Π_u, υ″ = 6) from the O₃ + C₂H₂ reaction. CH(²Δ), OH(²Σ⁺) and OH(²Π_j, υ ? 9) emissions were identified from the O₃ + C₃H₄ reaction in addition to the CH₂O(¹A″) emission previously reported.     

Sensitized fluorescence (A 1Π−X 1Σ+ and b 3Σ+−a 3Π) of 12C16O, 13C16O,and 12C18O by Kr(3P1) and Kr(1P1)

The Kr(³P₁) state was shown to excite preferentially the A ¹Π υ′ = 13 state of ¹³C¹⁶O and ¹²C¹⁸O by a resonance process. No resonance energy transfer was observed between Kr(³P₁) and ¹²C¹⁶O. The Kr(¹P₁) state was shown to excite the b ³Σ⁺ υ′ = O and υ′= 1 states of ¹²C¹⁶O, ¹³C¹³O by a non-resonance process.     

Structure and spectra of 1,3-dioxanes. microwave spectrum,structural parameters and <Emphasis Type="Italic">ab initio</Emphasis> calculations of 1,3-dioxane

Microwave spectra of the 1,3-dioxane molecule (C₄H₈O₂) with the main isotopic composition and four its isotopomers (¹³C(2)¹²C₃H₈ ¹⁶O₂, ¹³C(4)¹²C₃H₈ ¹⁶O₂, ¹³C(5)¹²C₃H₈ ¹⁶O₂, ¹⁸O(1)¹²C₄H₈ ¹⁶O) are investigated in a frequency range of 28–44 GHz. Rotational transitions of b-and c-types with 2 ≤ J ≤ 5 are identified. Rotational constants, quartic constants of centrifugal distortion, isotope-substituted r _s-and effective r ₀-structures of the molecule ring are determined. Experimental data are compared to the results of quantum chemical calculations of different levels.     

Nitrogen-14 quadrupole coupling constants in N2O3 by isotopic labelling

Several microwave transitions of O¹⁵N…NO₂ and ON…¹⁵NO₂ have been measured under high resolution using a pulsed-nozzle Fourier transform spectrometer. The ¹⁴N quadrupole coupling constants in the inertial axis system have been determined for both nitrogen atoms. The quadrupole coupling constants for ON …¹⁵NO₂ are eQq_aa = −0.5203(20) and eQq_bb = −4.1981(19) MHz, and for O¹⁵N…NO₂ are eQq_aa= −1.7999(13) and eQq_bb = 0.0808(17) MHz. The ¹⁴N quadrpole coupling constants determined by Kukolich for the main species ON…NO₂ should be reversed with respect to the NO and NO₂ groups. Combining the present data with the main species constants allows the complete quadrupole coupling tensor to be estimated for the NO₂ group; the tensor in N₂O₃ lies within 2° of the N…N bond direction and within 0.4° of the bisector of the ONO angle. Spin-rotation effects are significant for nitrogen in the NO group; C_aa is determined to be 8 ± 2 kHz for ¹⁴N in ON…¹⁵NO₂ and −15 ± 3 kHz for ¹⁵N obtained directly from splittings in the spectrum of O¹⁵N… ¹⁵NO₂.     

C2O(Ã 3Πi↔-~X3Σ−: laser induced excitation and fluorescence spectra

Laser induced fluorescence of C₂O is observed following the 266 nm laser photodissociation Of C₃O₂. Excitation spectra of C₂O(óΠ_i?-~X³Σ^? are consistent with previous absorption studies of C₂O. A number of new transitions are identified and assigned. Fluorescence spectra have been recorded following single vibrational level laser excitation. Bands are assigned to ground state vibrational progressions. Values of 1967 and 1063 cm^?1 are found for υ₁″ and υ₃″ stretching vibrations in the X?³Σ ^? state. A subband structure in the fluorescence spectrum is observed and discussed.     

Microwave spectrum,centrifugal perturbation,and dipole moment of acetyl chloride

An analysis of the microwave spectrum of acetyl chloride (¹²CH₃ ¹²C¹⁶O³⁵Cl) in the ground vibrational state allowed us to determine the quartic constants of centrifugal distortion and to refine the rotational constants and the constants of quadrupole coupling of³⁵Cl nuclei in this compound. The Stark effect of the 0–1₁₁ transition has been measured and analyzed. The components of the dipole moment have been determined: μ_a=1.047(10) D and μ_b=2.503(4) D. The total dipole moment of the moment of the molecule is 2.713(8) D. Ufa Scientific Center of Russian Academy of Sciences, Physics Department. Translated fromZhurnal Struktumoi Khimii, Vol. 36, No. 3, pp. 424–429, May–June, 1995. Translated by I. Izvekova     

Lifetimes of the vibronic Ã2A1 states of H2O+ and of the 3Πi (υ′ = 0) state of OH+

Using the delayed coincidence technique, lifetimes have been measured for some Σ and Π vibronic òA₁ states of H₂O⁺ and for the ³Π_i (υ′ = 0) state of OH⁺ by analysing the decay curves of the òA₁(0, υ′₂, 0) ? X?²B₁ (0, υ″₂, 0) and the ³Π_i(υ′ = 0) ? ³Σ^?(υ″ = 0) emission intensities respectively. The excited molecular ionic states are produced via excitation of H₂O molecules by 200 eV electrons. For H₂O⁺(òA₁) the vibronic Σ levels with υ′₂ = 13 and 15 and the vibronic Π levels with υ′₂ = 12 and 14 have been considered. The radiative lifetimes obtained for these levels have about the same value, namely 10.5(±1) × 10^?6 s. The radiative lifetime for the OH⁺(³Π_iυ′= 0) state is 2.5(±0.3) × 10^?6 s. The lifetimes found in this work for H₂O⁺(òA₁) and OH⁺(³Π_i,υ′= 0) are about ten and three times longer respectively than the corresponding lifetimes given by other investigators [1,2]. The probable reason for this discrepancy is that in the other experiments no attention has been paid to the presence of a large space charge effect. This effect is caused by the positive ions which are created by the primary electron beam.     

13C NMR coupling constants in delocalized organo-alkali metal compounds. Models of polymerization systems

2,5-Diphenyl-2,5-dipotassiohexane, 2-lithio-4,4-dimethyl-2-phenylpentane, and 1-lithio-2,5,5-trimethylhexene-2 have been prepared, all labelled with¹³C in the position adjacent to the alkali metal atom. The¹³C NMR spectra of these compounds have been measured and the¹³CC coupling constants found for the charged atom. The first two compounds have coupling constants consistent with an sp² hybridized C_α, with relatively little effect of the charge on the coupling constant. The third compound, when dissolved in either THF or benzene, gave much smaller coupling constants, which are more difficult to interpret.     

Mittlere Schwingungsamplituden,derBastiansen-Morino-Schrumpfungseffekt und thermodynamische Größen einiger isotopenmarkierter Moleküle des Kohlentrioxids

Mean amplitudes of vibration for the bonded as well as nonbonded atom pairs andBastiansen-Morino shrinkage effect for the isotopic species of carbon trioxide such as¹²C¹⁶O₃,¹²C¹⁸O₃, and¹³C¹⁶O₃ have been computed at the temperaturesT=298° K andT=500° K by the group theoretical method employing the symmetry coordinates. Molar thermodynamic functions have also been calculated for the temperature range 200–2000° K on the basis of a rigid rotator, harmonic oscillator model. Results are briefly discussed.     

Untersuchungen zum elektronischen einfluss von organylliganden: IV. 13C-NMR-spektroskopische untersuchung der gegenseitigen beeinflussung von organylliganden in triethylzinnorganylverbindungen

By means of ¹³C NMR spectroscopy, the coupling constants ¹J(¹¹⁹Sn¹³C_Et) of 18 compounds of the SnEt₃R type (R = organo group) have been measured. These coupling constants have been shown to reflect the change induced by R in the s-content of the tin hybrid orbitals of the SnCEt bonds. The series of the influence of R obtained on the basis of the coupling constant mentioned as a parameter is compared with a trans-influence series of R obtained on organo-mercury compounds. Occurring differences are attributed to different modes of bonding of the group R at the central atom.     

Vibrational lifetime measurements of matrix isolated molecules by an optical “double resonance” method

An optical-optical “double-resonance” experiment has been developed and successfully applied to the study of vibrational lifetimes. This pulsed dual laser technique should be applicable to all species possessing resolvable allowed vibronic transitions and it permits the direct measurement of vibrational lifetimes which, at present, may be as short as 20 μs. Application of this technique to the υ″ = 1 and υ″ = 2 states of matrix isolated C₂^? yields half lifes of 0.2 and 1.2 ms, respectively, in an argon matrix at 16K, and 0.3 and 1.3 ms in an N₂ matrix at 14K. No significant temperature variation of these rate constants has been found in the range 14 to 24 K. This is the first direct measurement of the vibrational lifetime of a homonuclear diatomic molecule isolated in a matrix environment.