800℃下在氩气中分解甲烷合成单壁碳纳米管反应中水的作用(英文)

pacc:8220,7125X TheeffectsofH2OtosynthesizingSWCNTs bydecomposingCH4inArat800℃werestudied byTEMandRamanscattering.Itisshownthat thewaterinducedintothereactinggas(therela tivehumidityisabout5%atroomtemperature)increasedthepercentagecompositionoftheSWC NTs…     

The angleICI Bending Satellites in the Millimeter-Wave Rotational Spectra of CH(2)I(2) and CD(2)I(2)

Rotational transitions in the first four excited states of the low-frequency angleICI bending mode, nu(4), have been assigned in the mm-wave rotational spectra of CH(2)I(2) and of CD(2)I(2). Measurements of transition frequencies, made over the frequency region 167-326 GHz and for J" up to 190, allowed determination of sextic level spectroscopic constants for all states. The changes in spectroscopic constants with vibrational excitation show very small anharmonicity, in spite of the very low frequency of this mode (121 cm(-1)). Vibrational excitation affects the moments of inertia in such a way that the planar moment P(b), about the plane perpendicular to both angleICI and angleHCH, is practically invariant. Vibrational change in P(c), the moment along the principal axis in the HCH plane and perpendicular to the angleHCH bisector, has been successfully reproduced with an ab initio harmonic force field so that there is no discernible vibrational change in angleHCH on excitation of angleICI. Finally, the change in P(a) leads to estimated vibrational change of +0.12 degrees in the value of angleICI itself. Copyright 2000 Academic Press.     

2-甲基蒽醌光敏氧化芳香类氨基酸的激光光解

以355 nm激光为激励光源,研究 2-甲基蒽醌(MAQ)光敏氧化芳香氨基酸(色氨酸、酪氨酸、苯丙氨酸)的光化学行为。在乙腈-水体积比1∶1的混合体系中,2-甲基蒽醌三重激发态(3MAQ*)的吸收峰位于390,450和590 nm,利用3MAQ*与电子给体的电子转移反应确定其阴离子自由基的特征吸收峰为390和490 nm。2-甲基蒽醌与色氨酸、酪氨酸、苯丙氨酸的瞬态反应都显示随着590 nm激发三重态的衰减,出现490 nm 2-甲基蒽醌阴离子自由基的生成,并进一步确定了2-甲基蒽醌与色氨酸、酪氨酸和苯丙氨酸的电子转移反应的速率分别为3.0×109,1.1×109和1.8×108 L·mol-1·s-1。同时吉布斯自由能(ΔG)的计算结果也表明2-甲基蒽醌的激发三重态与色氨酸、酪氨酸、苯丙氨酸电子转移反应在热力学上是可行的。     

Single-molecule conductance determinations on HS(CH2)4O(CH2)4SH and HS(CH2)2O(CH2)2O(CH2)2SH, and comparison with alkanedithiols of the same length

The acetyl-protected, thiol-terminated ethers AcS(CH(2))(4)O(CH(2))(4)SAc and AcS(CH(2))(2)O(CH(2))(2)O(CH(2))(2)SAc have been synthesised, and a range of related scanning tunnelling microscopy (STM)-based methods have been employed to fabricate and electrically characterise gold | single molecule | gold junctions involving these molecules. The single-molecule conductance values obtained are consistently found to be substantially higher (by a factor of 2-3) than the conductances of analogous alkanedithiols of similar length (HS(CH(2))(9)SH and HS(CH(2))(8)SH, respectively). A rationalisation of these findings is suggested, namely that the lone pair electrons on the oxygen atoms are substantially closer in energy to the Fermi energy of the gold leads than are the occupied and unoccupied states of methylene chains, so that the ether oxygens behave in a manner analogous to 'wells' in a double-tunnelling-barrier system. In agreement with this suggestion, the current-voltage behaviour of the monoether can be fitted using the Simmons approach, and the barrier height is found to be significantly lower than for alkanedithiols of approximately the same length.     

CH3CH2+O(3P)反应机理的理论研究

利用abinitio方法对CH3CH2+O(3P)反应进行了理论研究,在MP2/6311+G(d,p)水平上优化得到了反应途径上的反应物、中间体、过渡态和产物的几何构型和谐振频率,并在QCISD(T)/6311+G(d,p)水平上进行单点能计算.计算结果表明:CH2O+CH3、CH3CHO+H和CH2CH2+OH是主要反应产物,其中CH2O+CH3主要来自反应通道A1:(R)→IM1→TS3→(A),CH3CHO+H主要来自反应通道B1:(R)→IM1→TS4→(B),CH2CH2+OH主要来自直接抽提反应通道C1和C2:(R)→TS1(TS2)→(C).计算结果同时表明该反应生成CO的通道能垒是非常高的,CO应该不是主要产物.     

CH3CH2+N(4S)反应机理的理论研究

利用abinitio方法对CH3CH2+N(4S)反应进行了理论研究,在MP2/6-311+G(d,p)水平上优化得到了反应途径上的反应物、中间体、过渡态和产物的几何构型和谐振频率,并在QCISD(T)/6-311+G(d,p)水平上进行单点能计算.计算结果表明,CH2CH2+3NH和H2CN+CH3是此反应主要产物,CH3CHN+H是此反应次要产物.产物CH2CH2+3NH主要来自直接氢抽提反应通道,H2CN+CH3来自加成-解离反应通道,CH3CHN+H来自加成-解离反应通道.     

Rovibrational Study of the CH(2) Wagging Fundamental of Monofluoroacetonitrile

The vapor-phase infrared spectrum of monofluoroacetonitrile (CH(2)FCN) has been recorded at high resolution in the nu(4) band region (1363-1398 cm(-1)) using a tunable diode laser spectrometer. A detailed assignment of the rotational structure of the expected a-/b-hybrid band has been made for a-type transitions with K(a)相似文献   

一类2(1H)-喹喔啉衍生物的紫外光谱研究

研究了一类喹喔啉衍生物 ,1 烷基 3 甲基 2 (1H) 喹喔啉 2 酮 (1 alkyl 3 methyl 2 (1H) quinoxalin 2 one,简称AMQ ,其中alkyl =H ,CH3,C2 H5,n C3H7,n C5H1 1 ,n C1 6 H33)的紫外吸收光谱。这类化合物可应用于药物 ,如用作α 氨基羟甲基异恶唑丙酸 (AMPA)受体拮抗剂、杀菌剂等 ;还可用作植物生长调节剂、荧光探针等领域。结果表明 :化合物中氮原子上烷基链的增长对该类喹喔啉衍生物的紫外吸收光谱基本没有影响 ,谱图中峰形大体相同。紫外吸收谱图中 ,在 32 7和 340nm左右有两个吸收强度相当的一对肩峰 ,2 80nm处有一个吸收强度稍弱的峰 ;340nm左右的吸收峰主要是n→Π 跃迁所致 ,其中也含有Π→Π 跃迁的成分 ;32 7和2 80nm左右强吸收峰是Π→Π 跃迁所致。     

Barriers to internal rotation and tunnelling splittings of the torsional states in the HO(CH2)OH,DO(CH2)OH and DO(CH2)OD molecules

Torsional states caused by vibrations of hydroxyl groups in the methanediol molecule and its two deuterated analogues – DO(CH₂)OH and DO(CH₂)OD were analysed at MP2/cc-pVTZ and CCSD(T)/cc-pVQZ levels of theory. In the first case, 2D PES and 2D surfaces of kinematic coefficients were calculated with geometry optimisation for all other geometric parameters, and in the second case, only the energy of optimised configurations at the MP2/cc-pVTZ level of theory was determined. Then 2D PES was recounted to the complete basis set (CBS) limit by extrapolating the results of calculations at the MP2/cc-pVTZ and MP2/cc-pVQZ levels of theory The calculated values were then averaged over four equivalent points on the coordinate plane. Hamiltonian matrices were constructed using DVR and Fourier methods. After their subsequent diagonalization, the energies of the stationary torsional states were computed. Their classification by C_2V(M) and C_S(M) molecular symmetry groups has been performed. The splitting values due to the tunnelling of the thirty most deeply located torsional states in the three studied molecules were also determined. The torsional states, internal rotation barriers, and tunnelling frequencies in the molecules of methanediol and hydrogen trioxide were compared.