The Rotational Spectrum of Fluoroethyne (HCCF) Revisited

The pure rotational spectrum of fluoroethyne (fluoroacetylene, HCCF) has been reinvestigated. Rotational transitions have been measured in the frequency range from 230 up to 510 GHz and assigned to the excited vibrational states (υ₃υ₄υ₅)=(000), (001), (002), (003), (010), (011), (012), (020), and (100). The analysis of the spectrum extends the spectroscopic data for HCCF by correcting and refining the rotational and rovibrational constants determined in our previous investigation.     

Rotational Spectrum of Vinylarsine

The rotational spectrum of vinylarsine in the ground state has been studied in the range 7–320 GHz. The spectra of asynconformer and agaucheconformer have been unambiguously assigned on the basis of the existence of ab-type or ac-type spectrum. Rotational constants, quartic, and some sextic centrifugal distortion constants were derived. For thesynform, measurements of lowJ^aR_0,1transitions in a pulsed-nozzle Fourier transform microwave spectrometer (FTMWS) enabled the determination of the diagonal elements of the quadrupole tensor, as well as two spin–rotation constants.Ab initiocalculations performed at the MP2 level using the 6-311++G(3df, 3pd) basis set reproduced experimental rotational constants within 0.2%.     

Rotational Spectrum of Sarin

As part of an effort to examine the possibility of using molecular-beam Fourier-transform microwave spectroscopy to unambiguously detect and monitor chemical warfare agents, we report the first observation and assignment of the rotational spectrum of the nerve agent Sarin (GB) (Methylphosphonofluoridic acid 1-methyl-ethyl ester, CAS #107-44-8) at frequencies between 10 and 22 GHz. Only one of the two low-energy conformers of this organophosphorus compound (C(4)H(10)FO(2)P) was observed in the rotationally cold (T(rot)<2 K) molecular beam. The experimental asymmetric-rotor ground-state rotational constants of this conformer are A=2874.0710(9) MHz, B=1168.5776(4) MHz, C=1056.3363(4) MHz (Type A standard uncertainties are given, i.e., 1sigma), as obtained from a least-squares analysis of 74 a-, b-, and c-type rotational transitions. Several of the transitions are split into doublets due to the internal rotation of the methyl group attached to the phosphorus. The three-fold-symmetry barrier to internal rotation estimated from these splittings is 677.0(4) cm(-1). Ab initio electronic structure calculations using Hartree-Fock, density functional, and Moller-Plesset perturbation theories have also been made. The structure of the lowest-energy conformer determined from a structural optimization at the MP2/6-311G(**) level of theory is consistent with our experimental findings. Copyright 2001 Academic Press.     

The Rotational Spectrum of H2Te

In the present work, we study the spectrum of the H₂Te molecule in the submillimeter-wave and far infrared region. An important aim of this investigation is the further experimental characterization of the anomalous “four-fold cluster effect” exhibited by the rotational energy levels in the vibrational ground state of H₂Te. The spectrum in the region 90–472 GHz was measured with a source-modulated millimeter-wave spectrometer and that between 600 and 1600 GHz with a far-infrared sideband spectrometer. The far infrared spectrum from 30 to 360 cm⁻¹was measured with a Bruker IFS 120 HR interferometer attached to a 3 m long cell. We have assigned 224 submillimeter-wave lines and 1695 FIR lines. These observed data were supplemented by a large number of ground state combination differences derived from rotation–vibration bands of H₂Te, and the resulting large data set was analyzed by means of a modified Watson Hamiltonian. Accurate sets of rotational and centrifugal distortion constants for all eight tellurium isotopomers were obtained.     

Further Investigations of the ClO Rotational Spectrum

Pure rotational transitions of the chlorine monoxide radical have been observed up to v=2 in the X(1) (2)Pi(3/2) and X(2) (2)Pi(1/2) states and transitions of the (35)Cl(18)O isotopomer have been observed in natural abundance. Additionally, rotational transitions for levels up to J'=115/2 have been measured in the far infrared. These data have been merged with the existing microwave, submillimeter, and high-resolution infrared transition frequencies and fit simultaneously with a set of isotopically independent parameters. Isotopic substitution of both the Cl and O atoms has enabled the first determination of the electron spin-rotation constant gamma=-296.0(43) MHz as well as the Born-Oppenheimer corrections to the rotational constants. Copyright 2001 Academic Press.     

The Rotational Spectrum of the p-Fluorotoluene- Argon van der Waals Complex

The microwave rotational spectrum of the p-fluorotoluene-argon van der Waals complex was analyzed with a molecular beam Fourier transform microwave spectrometer. In the frequency splitting of molecular transitions caused by the internal rotation of the methyl group with respect to the aromatic ring is contained the structure and barrier information. Elucidation is reduced by the analysis of internal rotors direction with respect to the principal axis system of the complex the number of possible solutions in the structure. An rs and r0 structure of the complex was calculated from these data. The argon is located 3.541(1) ? above the aromatic ring. By forming the complex, the barrier height of internal rotation is changed. An additional V3 term in the potential function occurs in the complex because the molecular symmetry of the p-fluorotoluene, containing a V6 but no V3 term, is reduced by the argon. For assumed V6 = 144.79(19) GHz or 57.777(76) J/mol, V3 is found to equal 552.0(10) GHz or 220.31(40) J/mol. Copyright 1999 Academic Press.     

Rotational Spectrum of Hydrazine in the Submillimeter Range

In the submillimeter range, from 345 to 410 GHz, 472 new rotational transitions in the vibrational ground state of hydrazine have been measured. The majority of recorded lines form eight K=2←1 Q-branches with J≤30, each branch being split due to internal rotation in hydrazine. New rotational transitions together with 443 known earlier have been fitted to an effective group-theoretical Hamiltonian originally developed by Hougen (J. T. Hougen, J. Mol. Spectrosc.89, 296-327 (1981)). A reasonable fit was obtained using several ΔK=0, ±1, ±2, and ±4 matrix elements. For all 915 rotational transitions an overall standard deviation of the fit of 0.59 MHz was obtained using 32 parameters. These were 14 asymmetric rotor constants, 16 NH₂ inversion parameters, and 2 internal rotation parameters.     

Free-Jet Rotational Spectrum and ab Initio Calculations of Formanilide

Formanilide has been investigated by free-jet millimeter-wave absorption spectroscopy. The rotational spectrum of the conformer with the formyl hydrogen anti to the phenyl group has been assigned. Several rotational transitions of the ground state have been measured for both normal and ND isotopic species. All the atoms of the peptidic group are coplanar to the ring. Copyright 2001 Academic Press.     

The Rotational Spectrum of Tricarbonyl(trans,trans-2,4-hexadiene) Iron

The microwave spectrum of tricarbonyl(trans,trans-2,4-hexadiene) iron has been recorded in the range from 3 to 22 GHz using a Balle-Flygare type Fourier transform microwave spectrometer. The b- and c-type spectrum for the (56)Fe and the (54)Fe isotopomer could be assigned. The internal rotation of the two equivalent methyl groups results in a fine structure of the rotational transitions which is analogous to that of 2,2-dimethyloxirane [H. Hartwig and H. Dreizler, Z. Naturforsch., A: Phys. Sci. 47, 1063-1066 (1992)] and cis-2,3-dimethyloxirane [H. Hartwig and H. Dreizler, Z. Naturforsch., A: Phys. Sci. 47, 1051-1057 (1992)]. Analyzing this fine structure yields the internal rotation barrier in addition to the rotational constants and the quartic centrifugal distortion constants. Copyright 2000 Academic Press.     

利用转动拉曼测量大气气溶胶后项散射比

利用大气的弹性散射信号与整个转动拉曼信号的比值,不需要假设任何的气溶胶的消光与后项散射比值,就可得到大气气溶胶的后项散射比。通常测量部分转动拉曼谱线之和代替全部转动拉曼谱线之和。全部的转动拉曼谱线之和是不依赖温度,但部分的转动拉曼谱线之和却是与温度有关的。因此,利用转动部分拉曼谱线之和反演大气气溶胶的后项散射比就会带来误差。模拟了随温度变化不同转动量子数的拉曼谱线之和,并且计算了由这些不同转动拉曼谱线之和反演大气气溶胶后项散射比的误差。然后文章提出了一种新的方法,不需要测量整个转动拉曼谱线之和,而只需要测量单条转动拉曼谱线及大气温度,就可以获得大气气溶胶的后项散射比。最后通过实验给出了实际测量的大气气溶胶的后项散射比的结果。     

高温下CO分子的振转跃迁光谱

采用近似方法计算了CO分子的总配分函数;利用该分子的偶极矩函数和在Morse近似下的波函数,计算了分子的振转跃迁矩阵元及在常温和高温下的吸收系数。计算结果表明,在常温(296 K)和高温下(3 000 K),计算结果与HITRAN数据库和文献值符合的很好,表明对分子总配分函数和振转跃迁矩阵元的计算是可靠的。并首次计算了CO分子在更高温度(4 000和6 000 K)下的吸收系数。     

Raman-Mie方法反演气溶胶后向散射系数

传统的Klett和Fernald反演气溶胶法依赖于消光系数和后向散射系数的假设关系,给反演结果带来误差。根据纯转动拉曼后向散射系数仅是大气温度和压强的函数,设计的Raman-Mie方法用米散射和纯转动拉曼回波信号结合探空温度和大气压强共同反演气溶胶后向散射系数。不仅消除了Klett和Fernald方法引入假设带来的误差,还可避免因几何因子修正带来的影响。最后将该方法用于实验室自行研制的拉曼-米散射激光雷达,反演出了大气气溶胶后向散射系数廓线,实验结果与Klett(Fernald)方法分别进行了比较。     

The Pure Rotational Spectrum, Geometry, and Hyperfine Constants of Hafnium Monosulfide, HfS

The pure rotational spectra of seven isotopomers of hafnium monosulfide have been measured for several vibrational states. For the most abundant isotopomer, ¹⁸⁰Hf³²S, the J=1 - 0, J=2 - 1, and J=3 - 2 transitions were recorded up to the sixth vibrationally excited state. The constants Y₀₁, Y₀₂, Y₁₁, Y₂₁, and Y₃₁ were determined via a multi-isotopomer fit to a Dunham-type expression. In the process of fitting the data it was necessary to include Born-Oppenheimer breakdown correction terms. The equilibrium internuclear distance has been evaluated. For both the ¹⁷⁷Hf³²S and ¹⁷⁹Hf³²S isotopomers, nuclear hyperfine structure due to the hafnium nucleus was observed and notably large Hf nuclear quadrupole coupling constants, eQq, were determined.     

2∽6 GHz范围内二苯并呋喃的纯旋转光谱

本文使用自己搭建的宽带啁啾脉冲傅里叶变换微波谱仪对二苯并呋喃在2∽6 GHz范围内的转动光谱的测量和归属. 对微波光谱的分析获得了40个b型跃迁的归属,精确地确定了旋转常数A=2278.19770(38) MHz、B=601.12248(10) MHz和C=475.753120(98) MHz.     

The Vacuum Ultraviolet Absorption Bands of the Pink Afterglow Spectrum of Molecular Nitrogen Revisited at High Resolution

The absorption spectrum of the pink afterglow of molecular nitrogen in the vacuum ultraviolet has been analyzed at high resolution. The spectrum exhibits hot bands involving vibrational levels of the electronic ground state as high as v" = 19. Experimentally determined term values are derived for v" = 0-19, of which v" = 16-19 were before now poorly known. Copyright 1999 Academic Press.