First detection of the Cs symmetric isomer of carbon hexaoxide (CO6) at 10 K

Carbon oxides of the form CO_n (n = 2–8) have long been known as important molecules in atmospheric and solid state chemical reactions. Here, we report on the first infrared spectroscopic detection of the cyclic (C_s) isomer of carbon hexaoxide (¹²C¹⁶O₆) via its ν₁ vibrational mode centered around 1876 cm⁻¹ under matrix isolation conditions; the identification of the ¹²C¹⁸O₆, ¹³C¹⁶O₆, and ¹³C¹⁸O₆, isotopologues supported by ab initio calculations confirm the assignments. We also discuss possible formation routes of this molecule.     

Determination of calcium, iron and zinc in milk powder by reaction cell inductively coupled plasma mass spectrometry

An inductively coupled plasma mass spectrometer (ICP-MS) equipped with a dynamic reaction cell™ (DRC) was used for the determination of Ca, Fe and Zn in milk powder samples. The effect of the operating conditions of the DRC system was studied to get the best signal-to-noise (S/N) ratio. The potentially interfering ⁴⁰Ar⁺, ⁴⁰Ar¹⁶O⁺, ⁴⁰Ca¹⁶O⁺, ⁴⁸Ca¹⁶O⁺ and ³²S¹⁶O¹⁶O⁺ at the masses m/z 40, 56 and 64 were reduced in intensity significantly by using CH₄ as the reaction cell gas in the DRC while a q-value of 0.7 was used. The limits of detection for ⁴⁰Ca, ⁵⁶Fe and ⁶⁴Zn estimated from the external calibration graphs were 1, 0.01 and 0.001 ng ml⁻¹, respectively, which correspond to 1000, 10 and 1 ng g⁻¹ in the original powder sample. This method was applied to the determination of Ca, Fe and Zn in NIST SRM 1549 non-fat milk powder and two milk powder samples purchased locally. The results for the reference sample agreed satisfactorily with the reference values; the accuracy of the determination was better than 3.8, 18 and 2.2% for Ca, Fe and Zn, respectively. The results for which no reference value was available were also found to be in good agreement between different isotopes. Precision (R.S.D.) between sample replicates was better than 10% for all the determinations.     

Removal of interferences in the speciation of chromium using an octopole reaction system in ion chromatography with inductively coupled plasma mass spectrometry

When inductively coupled plasma mass spectrometry (ICP-MS) is used for the detection of ⁵²Cr (83.8%) species in ion chromatography (IC), interference from polyatomic ions such as ⁴⁰Ar¹²C⁺ and ³⁵Cl¹⁶O¹H⁺, often occurs due to their mass at m/z 52. To address the issue, an octopole reaction system (ORS) in ICP-MS, including He and H₂ modes, was used to determine whether the background and interference from polyatomic ions could be reduced in the detection of ⁵²Cr. Compared to standard mode, the polyatomic ions were reduced by either He or H₂; for example, more than 97 and 98% of ³⁵Cl was removed using a He and H₂ tune, respectively. However, the detection sensitivity for ⁵²Cr was decreased, for example, the sensitivity was 27.95 and 67.02% of the standard mode for Cr(EDTA)₂⁻using a He and H₂ tune, respectively. The H₂ tune is recommended for the detection of ⁵²Cr at a flow rate of 2.0 mL/min with detection limits in the range of 0.2–0.4 μg/L. The developed method was used to measure chromium speciation in waters containing high concentration of chloride.     

Ab initio study of sulfur isotope fractionation in the reaction of OCS with OH

The fractionation of sulfur isotopes in the gas-phase reaction of OCS with OH was calculated by ab initio methods. The first reaction step occurs through a carbon bonded OH–OCS transition state. The activation barrier is 18.4 kJ mol⁻¹ (CCSD(T)/aug-cc-pVDZ level plus zero-point energy) relative to the reactants. Fractionation constants are −1.4, −2.6 and −6.3‰ for ³³S, ³⁴S and ³⁶S respectively. These results bring new insight regarding the origin of stratospheric sulfate aerosols, including the identification of characteristic isotopic fractionations in the lower and middle stratosphere.     

SO分子势能曲线及振动能级的从头算研究

用ab initioMRD-CI方法研究了SO分子的基态X³Σ^-及激发态a¹Δ,b¹Σ⁺,A³Π,c¹Π,d¹Σ^-的势能曲线.结果表明,前4个电子态的平衡键长与实验结果吻合得很好,振动能级和转动常数的从头算计算结果也与已观测到的数据较吻合.此外,还对同位素取代物³⁴S¹⁶O和³²S¹⁸O的振动能级和转动常数进行了讨论.     

Rotational spectroscopy of the isotopic species of silicon monosulfide, SiS

Pure rotational transitions of silicon monosulfide ((28)Si(32)S) and its rare isotopic species have been observed in their ground as well as vibrationally excited states by employing Fourier transform microwave (FTMW) spectroscopy of a supersonic molecular beam at centimetre wavelengths (13-37 GHz) and by using long-path absorption spectroscopy at millimetre and submillimetre wavelengths (127-925 GHz). The latter measurements include 91 transition frequencies for (28)Si(32)S, (28)Si(33)S, (28)Si(34)S, (29)Si(32)S and (30)Si(32)S in upsilon = 0, as well as 5 lines for (28)Si(32)S in upsilon = 1, with rotational quantum numbers J'< or = 52. The centimetre-wave measurements include more than 300 newly recorded lines. Together with previous data they result in almost 600 transitions (J' = 0 and 1) from all twelve possible isotopic species, including (29)Si(36)S and (30)Si(36)S, which have fractional abundances of about 7 x 10(-6) and 4.5 x 10(-6), respectively. Rotational transitions were observed from upsilon = 0 for the least abundant isotopic species to as high as upsilon = 51 for the main species. Owing to the high spectral resolution of the FTMW spectrometer, hyperfine structure from the nuclear electric quadrupole moment of (33)S was resolved for species containing this isotope, as was much smaller nuclear spin-rotation splitting for isotopic species involving (29)Si. By combining the measurements here with previously published microwave and infrared data in one global fit, an improved set of spectroscopic parameters for SiS has been derived which include several terms describing the breakdown of the Born-Oppenheimer approximation. With this parameter set, highly accurate rotational frequencies for this important astronomical molecule can now be predicted well into the terahertz region.     

Penning electron spectra from ionization of hydrogen atoms by He(2S) and He(2S) metastables

Separate Penning electron spectra were measured resulting from the ionization of H atoms by He(2¹S) and He(2³S) metastables in thermal collisions. From these results potential parameters of the diatomics He(2¹S)-H(²S) (²Σ) and He(2³S)-H(²S) (²Σ) as well as the cross-section ratio σ(singlet)/σ(triplet) are derived.     

Rotational excitation of ions produced by the He(2 S) Penning ionization of CO and N2

Rotational-state distributions of the CO⁺ (A–X, B–X) and N₂⁺(B–X) emissions produced by the collisions of He(2 ³S) with CO and N₂ were studied in the collision energy (E_R range 100–200 meV. The rotational populations of the emitting states can be fitte by single Boltzmann temperatures (T_R. The T_R (320 ± 30 K) for the ν′ = 3 and 4 levels of the CO⁺ (A²Π) state are nearly independent of, or slightly increase with, E_R, while T_R for the CO⁺(B²Σ⁺, ν′ = 0) state increases rapidly with E_R.The T_R (430 ± 20 K) for the N₂⁺(B²Σ⁺, ν′ = 0) state is nearly independent or slightly decreases with increasing E_R. Interactions providing these trends are discussed.     

Molecules in high spin states II: the pure rotational spectrum of MnF (XΣ)

The pure rotational spectrum of MnF has been measured in its X⁷Σ⁺ ground state using millimeter/sub-millimeter direct absorption methods. Five and six rotational transitions, respectively, were recorded for this radical in its v=0 and v=1 states in the range 338–630 GHz. MnF was created from SF₆ and manganese vapor, produced in a Broida-type oven. The species exhibited a complex pattern where the fine and ⁵⁵Mn and ¹⁹F hyperfine structures are intermixed. Rotational, spin–rotation, spin–spin and hyperfine parameters have been determined for MnF. These constants have been interpreted in terms of bonding and electronic structure in metal fluorides.     

Matrixreaktion von GaF mit o-atomen: ir-spektrum von OGaF

It is possible to synthesize OGaF in an argon matrix by co-condensation of GaF with O atoms. The stretching vibrations of this compound are found at 943 and 690 cm⁻¹ (¹⁶O⁶⁹GaF). An exact calculation of the force field is possible with the aid of the observed ¹⁶O/¹⁸O and ⁶⁹Ga/⁷¹Ga shifts. The following force constants are found: f(GaO) = 6.32; f(GaF) = 4.69; f(GaO/GaF) = −0.1 [10²Nm⁻¹]     

Theoretical study on reaction mechanism of the vinyl radical with nitrogen atom

The complex triplet potential energy surface of the C₂H₃N system is investigated at the UB3LYP and CCSD(T) (single-point) levels in order to explore the possible reaction mechanism of C₂H₃ radical with N(⁴S). Eleven minimum isomers and 18 transition states are located. Possible energetically allowed reaction pathways leading to various low-lying dissociation products are obtained. Starting from the energy-rich reactant C₂H₃+N(⁴S), the first step is the attack of the N atom on the C atom having one H atom attached in C₂H₃ radical and form the intermediate C₂H₃N(1). The associated intermediate 1 can lead to product P₁ CH₂CN+H and P₂ ³CH₂+³HCN by the cleavage of C–H bond and C–C bond, respectively. The most favorable pathway for the C₂H₃+N(⁴S) reaction is the channel leading to P₁, which is preferred to that of P₂ due to the comparative lower energy barrier. The formation of P₃ ³C₂H₂+³NH through hydrogen-abstraction mechanism is also feasible, especially at high temperature. The other pathways are less competitive comparatively.     

Microwave investigation of the CO-CH4 van der Waals complex

Rotational spectra of eight isotopomers of the weakly bound van der Waals complex CO-CH4 were recorded in the frequency range from 4 to 19 GHz using a pulsed molecular beam Fourier transform microwave spectrometer. For the isotopomers containing methane monomers of Td symmetry, namely, 12C16O-12CH4, 12C16O-13CH4, 12C16O-12CD4, 13C16O-12CH4, and 13C18O-12CH4, three rotational progressions were observed that correlate to the jm=0, 1, and 2 rotational levels of free methane. For those containing partially deuterated methane monomers with C3V symmetry, namely, 12C16O-12CH3D and 12C16O-12CHD3, only two progressions were recorded, correlating to the jk=0(0) and 1(1) rotational levels of free CH3D and CHD3, respectively. The van der Waals bond distance R, intermolecular stretching frequency nus, and the corresponding stretching force constant ks were derived from the obtained spectroscopic results. The results obtained for the jm=0 ground state are compared to the previous infrared and millimeter wave data. A 17O nuclear quadrupole coupling constant was determined from the resolved hyperfine structure of 13C17O-12CH4 and was used to obtain angular information about the carbon monoxide subunit. A Coriolis interaction was deduced from the irregular spectral pattern involving levels with jm=1. Qualitative information about the extent of the perturbation was obtained from a comparison of spectroscopic constants of different isotopomers.     

Heavy atom structure and conformer stabilities of cyclopropyl carbinol from rotational spectroscopy and ab initio calculations

A remeasurement of the rotational spectra of the normal and hydroxyl deuterated isotopomers of cyclopropyl carbinol (cyclopropane methanol, (CH₂)₂CH(CH₂OH)) using Fourier-transform microwave spectroscopy has provided refined rotational constants and centrifugal distortion constants for this molecule. Rotational constants for an additional four singly substituted ¹³C isotopomers, the OD isotopomer, and the ¹⁸O isotopomer are consistent with a conformer in which the OH group forms an intramolecular hydrogen bond with the edge of the cyclopropyl ring. The observed a-type transition frequencies for the normal and deuterated species are in reasonable agreement with a previous microwave study (although some frequencies differ by several hundred kilohertz), but the few b- and c-type lines that were measured in the range of our spectrometer were found to differ by several megahertz from the previous literature measurements, leading to A rotational constants that differ significantly from those reported previously. The refined rotational constants for the normal isotopic species are A=12470.7795(23) MHz, B=3236.4678(7) MHz, C=2894.4831(7) MHz, while those of the deuterated species are A=12069.2653(24) MHz, B=3177.1540(8) MHz and C=2826.2658(7) MHz. Results of ab initio optimizations on seven conformers for this molecule carried out at the MP2/6-311+G(d,p) level will be compared with the experimentally determined structural parameters.     

The dynamics of the CH3CN molecule in the isotropic phase and in a nematic solution

NMR lineshape studies of acelonitrile in the isotropic and the liquid-crystalline nematic phase of PCH have been performed. The scalar relaxation of the second kind due to the presence of the ¹⁴N quadrupolar nucleus has been confirmed as the most important relaxation mechanism for this molecule in both the isotropic and the anisotropic phase. It has been found largely responsible for the selective broadening on ¹³C and ¹H transitions. A minor contribution arising from intramolecular dipolar relaxation mechanism has also been investigated. Linewidth analysis of the NMR spectra allowed us to determine the quadrupolar relaxation time T_IN of the ¹⁴N nucleus. This is connected to the correlation time for rotational diffusion perpendicular to the molecular symmetry axis. A possible explanation of a residual selective broadeining which effects the ¹³C and ¹H NMR transitions and is not taken into account by this mechanism, is also given.     

Formation Mechanism and Emission Spectrum of AlO Radicals in Reaction of Laser－ablated Al Atom and Oxygen

IntroductionLaser ablation has been applied broadly toplasma production,cluster formation,nanometermaterial and thin film material preparation[1,2 ] .Us-ing spectroscopic technique and mass spectrometryto identify the transient species formed in the pro-cess could provide much useful information aboutthe prosperity ofplasma,the mechanism of materi-al growth[3 ,4] .Aluminum is an important metal material andwidely used in industry and daily life. To study thereaction mechanism of Al atoms with…     

ATP-GTP-BINDING PROTEINS AND ENDOGENOUS ADP-RIBOSYL TRANSFERASE IN Lemna paucicostata 441

Abstract— A crude extract containing membrane components of Lemna paucicostata was treated with 1% Lubrol PX and fractionated by gel nitration. Binding activities to non-hydrolyzable analogues of ATP, [³⁵S]ATPγS (adenosine 5'[;γ-thio]triphosphate) and that of GTP, [³⁵S]GTPγS (guanosine 5'[γ-thiojtriphosphate) were detected in some fractions, and these activities were prevented in the presence of 0.1 mM ATP or GTP. ATP and GTP were 2 to 3 orders of magnitude more effective than CTP or UTP in preventing this binding activity. These fractions showed ATPase and GTPase activities with 1 nM [γ-³²P]ATP or [γ–³²P]GTP substrate. Analyses by sodium dodecyl sulfate polyacrylamide gel electrophoresis of these fractions after binding with [³⁵S]ATPγS or [³⁵S]GTP-γ S revealed that these fractions contained [³⁵S]ATPγS and [³⁵S]GTPγS binding proteins with molecular weights of 53 000 and 60 000, respectively. Both of these proteins were [³²P]ADP-ribosylated by endogenous ADP-ribosyl transferase. Three proteins with molecular weights of 11 000, 12 000 and 13 000 which could bind [³⁵S]ATP7S or [-³⁵S]GTP-γ S were ADP-ribosylated by endogenous ADP-ribosyl transferase. Pertussis toxin stimulated ADP-ribosylation of these proteins. Four proteins with molecular weight of 37 000, 50 000, 80 000 and 115 000 with P^SS]ATP7S and [^,3S]GTP7S binding activities were also detected. The signal transduction of light to underlying clock mechanism in Lemna may be controlled by ATP-GTP-binding proteins and by the ADP-ribosylation of these proteins.     

Electronic spectra and transitions of the fullerene C60

Absorption spectra of C₆₀ have been measured in the ranges (a) 190–700 nm in n-hexane solutions at 300 K, (b) 390–700 nm in n-hexane and in 3-methylpentane solutions at 77 K. 40 vibronic bands were observed. They exhibit a large range of bandwidths and intensities, whose significance is discussed. Assignment of electronic transitions has been carried out using the results of theoretical calculations. Vibronic structures have been analyzed within the framework of theories of electronic transitions of polyatomic molecules applied to the I_h symmetry group. Nine allowed ¹T_1u−¹A_g transitions have been assigned in the 190–410 nm region. Observed and calculated allowed transition energies and oscillator strengths are compared. Detailed vibronic analyses of the 1 ¹T_1u−1 ¹A_g and 2 ¹T_1u−1 ¹A_g transitions illustrate the role of Jahn-Teller couplings. Orbitally forbidden singlet-singlet transitions are observed between 410 and 620 nm. Their vibronic structures were analyzed in terms of concurrent Herzberg-Teller and Jahn-Teller vibronic interactions. The 77 K spectra provided useful information on hot bands and on other aspects of the analyses. Vibronic bands belonging to triplet←singlet transitions were detected between 620 and 700 nm.     

Kinetic processes of Hg6s6p(P1) in xenon

The principal route for decay of Hg 6s6p(³P₁) in xenon is shown to be bimolecular deactivation to the mercury ground state, with rate coefficient 9.1 × 10⁻¹³ cm³ molecule⁻¹ s⁻¹; relaxation to the ³P₀ state plays a negligible role. The equilibrium constant of the reaction Hg(³P₁) + Xe HgXe(A ³O⁺), has been recorded as 1.73 × 10⁻²⁰ cm³ molecule⁻¹ at 293 K.     

Novel cyclopentadienyl silanes and disilanes: synthesis, structure and gas-phase pyrolysis

The new chloro(cyclopentadienyl)silanes Cp′SiH_yCl_3−y (Cp′=Me₄EtC₅, y=1: 1; Cp′=Me₄C₅H, y=1: 2; y=0: 3; Cp′=Me₃C₅H₂, y=1: 4 and pentachloro(cyclopentadienyl)disilanes Cp′Si₂Cl₅ (Cp′=Me₅C₅ 5, Me₄EtC₅ 6, Me₄C₅H 7, Me₃C₅H₂ 8, Me₃SiC₅H₄ 9) are synthesized in good yields via metathesis reactions. Treatment of 1–9 with LiAlH₄ leads under Cl–H exchange to the hydridosilyl compounds Cp′SiH₃ (Cp′=Me₄EtC₅ 10, Me₄C₅H 11, Me₃C₅H₂ 12) and to the hydridodisilanyl compounds Cp′Si₂H₅ (Cp′=Me₅C₅ 13, Me₄EtC₅ 14, Me₄C₅H 15, Me₃C₅H₂ 16, Me₃SiC₅H₄ 17). Complexes 1–17 are characterized by ¹H, ¹³C, and ²⁹Si-NMR spectroscopy, IR spectroscopy, mass spectrometry and CH-analysis. The structures of 6, 7 and 9 are determined by single-crystal X-ray diffraction analysis. Pyrolysis studies of the cyclopentadienylsilanes 10–12 and disilanes 13–17 show their suitability as precursors in the MOCVD process.     

新的醚链双生物碱尖叶唐松草阿原碱的结构测定

从尖叶唐松草〔Thalictrumacutifolium(Hand.Mazz.)Boivin〕根分离得到一种新生物碱(尖叶唐松草阿原碱).通过IR,MS,¹HNMR,¹³CNMR,2DNMR(包括¹H-¹HCOSY,¹³C-¹HCOSY,NOESY和HMBC)测定了其化学结构,发现由阿朴菲和原小蘖碱通过醚链连接.对多种肿瘤细胞的生长有抑制作用,并有凋亡现象出现,而且对正常细胞的毒性较小