Br2偶宇称里德堡态的转动结构和电子角动量

由（２＋１）多光子电离方法获得溴分子６８８００－６９６００ｃｍ＾－１范围内的［ΠΠ／２］４ｄ偶宇称里德堡态转动激发光谱，通过对转动光谱的分析，确定了转动常数，Ｂ８１－８１＝０．０８６８８。并对电子角动量进行了标定，角动量Ω＝１。     

Transition from molecular complex to quantum solvation in 4HeNOCS

We present fully quantum calculations of the rotational energy levels and spectroscopic rotational constants of the linear OCS molecule in variable size clusters of 4He. The rotational constants of OCS are found to decrease monotonically from the gas phase value as the number of helium atoms increases to N=6, after which the average constant increases to saturation at the large droplet value by N=20. The minimum is shown to indicate a transition from a molecular complex to a quantum solvated molecule, with the former characterized by floppy but near rigid behavior, while the latter is characterized by nonzero permutation exchanges and a smaller extent of rigid coupling.     

Cosmic microwave background polarization signals from tangled magnetic fields

Tangled, primordial cosmic magnetic fields create small rotational velocity perturbations on the last scattering surface of the cosmic microwave background radiation. For fields which redshift to a present value of B0 = 3 x 10(-9) G, these vector modes are shown to generate polarization anisotropies of order 0.1-4 microK on small angular scales (500相似文献   

Microwave Spectrum of 2-Methylcyclohexanone

The five lowest J rotational transitions of (13)C(16)O have been measured by saturation-dip spectroscopy to an accuracy of about 2 kHz, employing phase-stabilized backward-wave oscillators (BWOs). These highly precise measurements cover the transitions from J = 2 <-- 1 to J = 6 <-- 5 with frequencies ranging from 220 to 661 GHz. For each of the five observed rotational transitions, the narrow linewidths of the saturation dips (about 20 kHz) permitted the resolution of the hyperfine splitting for the first time. This splitting is caused by the (13)C-nuclear spin-rotation interaction yielding a value for the nuclear spin-rotation coupling constant of C(I)((13)C(16)O). If combined with the beam measurements (C(I)((13)C(16)O) = 32.63(10) kHz), a slight J-dependence of the spin-rotation coupling constant can be determined (C(J) = 30 +/- 13 Hz). In addition, we have measured in the Doppler-limited mode several higher J rotational line positions of (13)C(16)O up to 991 GHz with an accuracy of 5 kHz. The two line positions (J = 12 <-- 11 and J = 14 <-- 13) were recorded by multiplying BWO frequency with an accuracy of 100 kHz. The rotational transitions J = 17 <-- 16 and J = 18 <-- 17 were measured with an accuracy between 15 and 25 kHz by using the Cologne sideband spectrometer for terahertz applications COSSTA. Copyright 2000 Academic Press.     

The microwave spectrum of pyrrolidine

The rotational spectra of the normal and N-D isotopic species of pyrrolidine have been measured. The molecule exists in an envelope conformation, with the nitrogen atom out of the plane containing the carbon atoms and with the imino hydrogen in the axial position. The analysis of the rotational spectra of two and three vibrationally excited states for the normal and N-D isotopic species, respectively, indicates that both barriers to pseudorotation and to the imino hydrogen inversion are relatively high. Additionally, the N(14) quadrupole coupling constants have been determined.     

The Rotational Spectra, Isotopically Independent Parameters, and Interatomic Potentials for the X(1)(2)Pi(3/2) and X(2)(2)Pi(1/2) States of BrO

Observations of the rotational spectrum of BrO have been extended to include vibrational levels up to v = 8 in the X(1)(2)Pi(3/2) and v = 7 in the X(2)(2)Pi(1/2) states. The rotational spectra of isotopically enriched Br(18)O, X(1), v = 0, 1 and X(2), v = 0 have been observed as well. The spectra of all four isotopic species have been fit to a Hamiltonian in which the parameters have fixed isotopic ratios. An extensive set of isotopically independent parameters has been determined. Interatomic potentials have been derived for both the X(1) and X(2) states. The hyperfine constants and their vibrational dependencies have been determined more precisely and several of them have been determined for the first time. These are interpreted in terms of the electronic structure of the molecule. The isotope relations among the constants have provided a means of decorrelating the electron spin-rotation constant gamma from the fine-structure centrifugal distortion constant, A(D), and have allowed the first determination of an effective value for gamma. Copyright 2001 Academic Press.     

Dipole moment and far infra-red absorption of quinuclidine (1-aza-bicyclo-[2-2-2]-octane)

Incoherent quasi-elastic neutron-scattering spectra have been measured on powder samples of D-BPBAC in its smectic E, B and A phases using the high-resolution backscattering technique. The data have been analysed in terms of translational diffusion and a localized rotational motion. It has been found that the apparent translational diffusion constant has a temperature dependent value of ～1 × 10^-6 cm² s^-1 in the smectic A phase but is smaller by at least an order of magnitude in the smectic B and E phases. Comparison of the widths of the rotational components of the spectra with other measurements suggests that simple rotational models are not adequate to explain the experimental data.     

大气压空气纳秒脉冲阵列式线-线SDBD等离子体的电学及发射光谱特性研究

提出了一种阵列式线-线沿面介质阻挡放电结构,利用双极性高压纳秒脉冲电源,在大气压空气中激励产生了相对大面积的放电等离子体。其中,高压电极、地电极均为圆柱形金属,放电反应器由20组相间排列的阵列式线型高压电极和套有介质管的阵列式线型地电极组成。利用电压探头、电流探头、示波器等测量了放电电压和放电总电流,并计算得出了放电的实际电流。利用光纤、光栅光谱仪、CCD等测量了波长范围在300～440 nm和766～778 nm的发射光谱,即氮分子第二正带N₂ (C3Π_u→B3Π_g)包括Δν= +1, 0, -1, -2, -3、氮分子离子第一负带N+₂(B2Σ+_u→X2Σ+_g),N₂ (B3Π_g→A3Σ+_u)和O (3p5P→3s5S₂)的发射光谱。比较了氮分子第二正带N₂ (C3Π_u→B3Π_g)的各个振动峰和各个活性物种的发射光谱强度,以及这些发射光谱强度随着脉冲峰值电压的变化。测量了N₂(C3Π_u→B3Π_g, 0-0)的二次、三次衍射光谱,与原始光谱在转动带、背景光谱等方面进行了比较,并计算了二次衍射和原始光谱之间的峰值比。利用氮分子第二正带N₂ (C3Π_u→B3Π_g, Δν=+1, 0, -1, -2)和氮分子离子第一负带N+₂ (B2Σ+_u→X2Σ+_g, 0-0)模拟了等离子体的转动温度和振动温度,对模拟结果进行了比较,并研究了脉冲峰值电压对等离子体振动温度和转动温度的影响。通过测量放电的电压和计算得到的放电电流发现,当脉冲峰值电压为22 kV,脉冲重复频率为150 Hz时,阵列式线-线沿面介质阻挡放电的放电电流在正脉冲、负脉冲两个方向上均可达75 A左右。通过诊断放电等离子体的发射光谱发现,在测量的波长范围内,放电产生的活性物种主要有氮分子第二正带N₂ (C3Π_u→B3Π_g)、氮分子离子第一负带N+₂(B2Σ+_u→X2Σ+_g),N₂ (B3Π_g→A3Σ+_u)和O (3p5P→3s5S₂)。在脉冲峰值电压22～36 kV的变化范围内,氮分子第二正带N₂(C3Π_u→B3Π_g, 0-0)的发射光谱强度始终保持最强,N₂ (B3Π_g→A3Σ+_u)次之,而氮分子离子第一负带N+₂(B2Σ+_u→X2Σ+_g)和O (3p5P→3s5S₂)的发射光谱强度较弱。同时,当脉冲峰值电压升高时,氮分子第二正带N₂ (C3Π_u→B3Π_g)的所有振动峰,以及氮分子离子第一负带N+₂(B2Σ+_u→X2Σ+_g),N₂ (B3Π_g→A3Σ+_u)和O (3p5P→3s5S₂)的发射光谱强度均随之升高。通过比较氮分子第二正带N₂(C3Π_u→B3Π_g, 0-0)的原始、二次衍射、三次衍射光谱发现,二次、三次衍射光谱的转动带更清晰,但三次衍射光谱的背景更强,因此氮分子第二正带N₂(C3Π_u→B3Π_g)的二次衍射光谱更有利于模拟等离子体的转动温度。通过比较模拟得到的振动温度和转动温度发现,氮分子第二正带N₂ (C3Π_u→B3Π_g, Δν=-2)在N₂ (C3Π_u→B3Π_g)四个谱带Δν=+1, 0, -1, -2中最适于模拟等离子体振动温度,而利用氮分子离子第一负带N+₂ (B2Σ+_u→X2Σ+_g,0-0)模拟得到的等离子体转动温度要比N₂ (C3Π_u→B3Π_g, Δν=-2)的模拟结果高约10～15 K。同时,当脉冲峰值电压升高时,由N₂ (C3Π_u→B3Π_g, Δν=-2)和N+₂ (B2Σ+_u→X2Σ+_g, 0-0)模拟得到等离子体的转动温度均出现了略微上升的趋势,而利用N₂ (C3Π_u→B3Π_g, Δν=-2)模拟得出的振动温度则略微下降。     

Jet-Cooled Optical Spectroscopy of FeN between 16 300 and 21 600 cm(-1)

We report the first gas-phase spectroscopic study of iron mononitride (FeN). FeN molecules were generated by the reaction of laser-ablated Fe atoms with NH(3) under supersonic jet-cooled conditions. Laser-induced fluorescence excitation spectra were measured between 16 300 and 21 600 cm(-1), and rotational analyses have been performed for about 25 vibronic bands. The Omega value of the ground state has been determined to be 52, which could be the spin-orbit component of (2)Delta (ellipsis 1delta(3)9varsigma(2)) or (4)Pi (ellipsis 1delta(3)9varsigma(1)4pi(1)). The excited states in the visible absorption region show very complicated rovibronic structures due to heavy perturbations. Excited state lifetimes, (56)Fe(14)N/(56)Fe(15)N isotope shifts, and dispersed fluorescence spectra were measured for the majority of the bands, which were classified into the five Omega = 52-XOmega = 52 band systems. Copyright 2000 Academic Press.     

High resolution photoassociation spectra of an ultracold Cs2 long-range 0u＋ （6S1/2 ＋ 6P1/2） state＊

In this paper, ultracold cesium molecules are formed through photoassociation technology, which is carried out in a magneto-optical trap. High resolution photoassociaion spectra with the rotational progressions up to J = 7 are obtained. Three rovibrational levels of the long-range 0＋ state of Cs2 below the （6S1/2 ＋ 6P1/2） dissociation limit are specifically investigated. By fitting their binding energy intervals to the non-rigid rotational model, the rotational constant of the long- range 0u＋ state is determined. A proportional dependence of the value of the rotational constant on the vibrational quantum number is demonstrated.     

Spectroscopic exploration of atomic scale superfluidity in doped helium nanoclusters

We present high resolution spectra of He(N)-OCS clusters with N up to 39 in the microwave and 72 in the infrared regions, observed with apparatus-limited line widths of about 15 kHz and 0.001 cm(-1), respectively. The derived rotational constant, B (proportional to the inverse moment of inertia), passes through a minimum at N=9, then rises due to onset of superfluid effects, and exhibits broad oscillations with maxima at N=24, 47 and minima at 36, 62. We interpret these unexpected oscillations as a manifestation of the aufbau of a nonclassical helium solvation shell structure. These results bridge an important part of the gap between individual molecules and bulk matter with atom by atom resolution, providing new insight into microscopic superfluidity and a critical challenge for theory.     

Rotational spectrum and structure of Si3

The rotational spectrum of a pure silicon cluster, the Si3 trimer, has been observed for the first time. From the rotational constants of the normal and the 29Si and 30Si isotopic species, a precise geometrical structure has been derived: the trimer is an isosceles triangle with a bond to the apex Si of length 2.177(1) A and an apex angle of 78.10(3) degrees. The substantial inertial defect and fairly large centrifugal distortion suggest that the molecule possesses a shallow bending potential. Si3 is a good candidate for astronomical detection because radio lines of comparably massive silicon molecules (e.g., SiC2, SiC4, and SiS) are readily observed in at least one astronomical source. The rotational spectra of Si6, Si9, and even larger polar silicon clusters may be detectable with the present technique, as well as similar germanium clusters.     

紫外光区S_2分子激光诱导荧光光谱

利用真空脉冲放电超声射流气体束(H_2S/Ar~3%混合气体)的方法产生了气相S_2分子,并研究了30 400~34 400cm~(-1)范围内S_2分子的时间分辨和基态振动频率分辨的激光诱导荧光光谱,获得了184支谱带的高分辨率(0.1cm~(-1))和低分辨率(0.3cm~(-1))转动光谱。实验观测并归属了S_2分子B_u~(Σ-)-X~3Σ_g~-和B″~3Π_u-X~3Σ_g~-共84支振动跃迁,分析得到了激发态B~3Σ_u~-态ν=0~9和B″~3Π_u态ν=2~12的分子常数以及B~3Σ_u~-态的基态平衡分子构型。由于S_2分子B~3Σ_u~-与B″~3Π_u态之间存在微扰,这两个电子激发态的振动能级间隔、自旋分裂常数和自旋-轨道分裂常数变化不规律,转动跃迁强度和跃迁选择定则存在异常,利用~3Σ-~3Π的齐次微扰哈密顿量定性地对这些异常光谱进行了解释,进一步丰富了S_2分子紫外区低能电子激发态的信息。     

Study of the torsion-rotation Hamiltonian for symmetric tops using the millimeter wave spectrum of methyl silane

The torsion-rotation Hamiltonian for symmetric tops has been tested in methyl silane by combining recent anticrossing molecular beam measurements in the ground torsional state (v = 0) with pure rotational spectra taken for v as high as 4. The earlier microwave data set which consisted of J = 1 ← 0 and 2 ← 1 has been greatly extended by studying millimeter transitions for J = 4 ← 3, 5 ← 4, and 13 ← 12. An analysis of the 72 rotational frequencies for v ≤ 2 and the 15 anticrossing data for v = 0 yielded an excellent fit using 14 rotational, torsional, and distortion constants including the effective values for the A rotational constant and the barrier height V₃. No satisfactory fit could be obtained when the data set was extended to include measurements for (v = 3) or (v = 4). For each of these higher torsional levels, the difference between the observed frequencies and the predictions based on the best (v ≤ 2) constants can be expressed in terms of a shift δB_v in the B rotational constant, where δB_v is a smooth function of the torsional energy. This disagreement is of particular interest because it may result from the fact that the molecule passes from hindered to free rotation as v is increased from 2 to 4. The possibility of perturbation by a low-lying vibrational level is considered briefly. The information contained in the different types of spectra is discussed; the redundancy relations are treated and a Fourier expansion of the diagonal torsional matrix elements is introduced. For ¹²CH₃²⁹SiH₃, ¹²CH₃³⁰SiH₃, and ¹³CH₃²⁸SiH₃ pure rotational spectra for v = 0 were studied briefly in natural abundance. The results were combined with existing data for two deuterated symmetric rotors to obtain a structure based only on symmetric top rotational constants.     

Study on high-temperature spectra of asymptotic asymmetric-top radical SiO2

Total internal partition sums are calculated in the product approximation at temperatures up to 6000 K for the asymptotic asymmetric-top SiO2 molecule.The rotational partition function and the vibrational partition function are calculated with the rigid-top model and in the harmonic oscillator approximation,respectively.Our values of the total internal partition sums are consistent with the calculated value in the Gaussian program within 0.137% at 296 K.Using the calculated partition functions and the rotationless transition dipole moment squared as a constant,we calculate the line intensities of 001-000 band of SiO2 at normal,medium and high temperatures.Simulated spectra of the 001-000 band of the asymptotic asymmetric-top SiO2 molecule at 2000,5000 and 6000 K are also obtained.     

MAS NMR with and without double-quantum filtration at and near the n=0 rotational resonance condition

Spectral lineshapes of MAS NMR spectra of dipolar (re)coupled spin pairs exhibiting considerable chemical shielding anisotropies at and near the so-called n=0 rotational resonance (R2) condition are considered. The n=0 R2 condition is found to be not extremely sharp. Anisotropic interaction parameters such as chemical shielding tensor orientations and the magnitude of the dipolar coupling constant remain sensitively encoded in such lineshapes even when differences in isotropic chemical shielding values of up to 400 Hz (corresponding to ca. half the size of the dipolar coupling constant) are present. Additional double-quantum filtration (DQF) may enhance the sensitivity of spectral lineshapes to anisotropic interaction parameters for even larger differences in isotropic chemical shielding values. The dependence of the DQF efficiency on spin-system parameters as well as on external parameters (Larmor and MAS frequencies) is investigated. Away from R2 conditions a trend to lower DQF efficiencies is found whereas some spin-system parameters are more sensitively encoded in the corresponding spectral lineshapes. Our study is based on numerical simulations, with the known parameters of the 31P spin pair in Na4P2O7.10H2O representing our model case.     

High Resolution FTIR Study on NH(2)Cl Molecule: Inversion and Anharmonicity

The high-resolution FTIR absorption spectra of the NH(2)Cl molecule have been measured in the region 500-3600 cm(-1). The rotational structures of all the fundamental bands and a number of overtone and combination bands have been analyzed. Every rotational line of the observed bands except the NH(2) twisting and stretching fundamental bands splits into two components due to the amino inversion motion. The vibrational anharmonicity and the direction of the transition moments have been studied with the help of B3LYP/6-31++G(**) calculations. The amount of inversion splitting depends on the molecular rotation, and the J,K-dependence of the inversion splitting has been determined. Copyright 2001 Academic Press.     

2-三氟甲基吡啶的转动光谱及分子结构研究

本文测定了2-三氟甲基吡啶在2∽20 GHz频率范围内的高分辨转动光谱. 测定了转动常数、¹⁴N核四极耦合常数及离心畸变常数等一系列光谱参数. 同时还在自然丰度下测定了5个¹³C和1个¹⁴N单取代同位素异数体的光谱数据. 实验结果结合从头算准确地推导出2-三氟甲基吡啶的骨架结构. 实验测得同位素异数体的平面转动惯量P_cc数值均为44.46 u?²，表明此分子具有C_s对称性. 此外，本文计算了吡啶、2-氟吡啶、2-甲基吡啶和2-三氟甲基吡啶的分子表面静电势，以此分析了三氟甲基的取代对电子分布的影响.     

Oxygen concentration and temperature measurements in N2–O2 mixtures using rotational coherent anti-Stokes Raman spectroscopy

The accuracy and precision of oxygen concentration and temperature measured by dual-broadband rotational Coherent Anti-Stokes Raman Spectroscopy (CARS) were investigated in nitrogen-oxygen mixtures at atmospheric pressure and temperatures between 290 and 1410 K. The relative standard deviation of temperatures evaluated from pure oxygen rotational CARS spectra was found to be around 5%, and the mean temperature was the same as for nitrogen CARS spectra, except for temperatures above 1000 K, where the temperature was 120 K below the correct value. The in situ calibrated oxygen concentrations were within 10% of the correct value, with a standard deviation of around 1.2% for the mixtures of 12 and 20% oxygen in nitrogen. For the lowest oxygen concentrations considered in this study (2 and 4%), the systematic errors in the evaluated concentrations were very large, and the standard deviation of repeated single-shot measurements was above 2%. However, employing weighting in the spectral fitting routine reduced the errors in the concentration and the single-shot standard deviation was lowered to 0.5%. Finally, it was shown that spectral interference (from oxygen) in a rotational CARS spectrum of nitrogen generally had little impact on the temperature evaluated from fitting the spectra to theoretical nitrogen spectra.     

Rotational Analysis of the Ground State and the Lowest Fundamentals nu(3), nu(5), and nu(6) of (13)CH(3)D

The nu(3), nu(5), and nu(6) fundamental bands of the (13)CH(3)D molecule have been studied with Fourier transform infrared spectroscopy. The spectra and results for the parent species (12)CH(3)D (O. N. Ulenikov, G. A. Onopenko, N. E. Tyabaeva, J. Schroderus, and S. Alanko, J. Mol. Spectrosc. 193, 249-259 (1999)) have been used to assign and analyze about 1900 lines belonging to the (13)CH(3)D isotopic species. About 850 ground state combination differences with DeltaK = 0 were calculated, which allowed us to determine the J-dependent ground state rotational constants. The K-dependent constants as well as those describing the a(1)-a(2) (K = 3) splitting were fixed to the values obtained for the (12)CH(3)D species. The (v(3) = 1), (v(5) = 1), and (v(6) = 1) states were fit simultaneously by including the intervibrational interactions in the Hamiltonian. The rotational energies, the rotational and centrifugal distortion constants, as well as the resonance parameters involving the three states have been determined and discussed. Copyright 2000 Academic Press.