The microwave spectrum of sodium tetrahydroborate NaBH4 in excited vibrational states: Coriolis interaction between the Na-BH4 stretching and the BH4 rocking vibrations

Two sets of vibrational satellites have been observed in the rotational spectrum of sodium tetrahydroborate NaBH₄, and have been assigned to the non-degenerate, Na—BH₄ stretching and the degenerate BH₄ rocking (or internal rotation) states. The observation was extended from the J = 11 ← 10 up to J = 20 ← 19 transitions. The vibrational satellites showed anomalous K structure; higher-K lines of the non-degenerate state appeared at higher frequencies, in reverse to those of the ground state, whereas the spectra in the degenerate state exhibited a K pattern similar to but somewhat more widely spread than that of the ground state. These anomalies are ascribed to the Coriolis interaction between the two excited vibrational states. The spectra observed were analysed using a C_3v symmetric-top rotational Hamiltonian, which took into account the Coriolis interaction explicitly. The A rotational constants, the energy difference δE between the two interacting vibrational states, and the first- and second-order Coriolis interaction constants have been derived.     

Cs(6 ~2D_(5/2))与H_2反应生成的CsH分子的转动和振动态分布

利用激光泵浦-探测技术,在样品池条件下,研究了Cs(6D5/2)态与H2反应生成的CsH分子基电子态的转动和振动的量子态分布。在Cs-H2混合蒸气中,脉冲激光双光子激发Cs(6D5/2)态,另一台调频脉冲激光器扫描CsHX1Σ+(v″,J″)→A1Σ+(v′,J′=J″±1)吸收线,发现CsH分子只有v″=0和1上的振动带上有布居而不布居在v″1的振动带上。v″=0和1上的转动带分布呈现单峰结构,其峰值位于J″=6～8处,转动带分布轮廓与池温下的统计分布接近。转动Boltzmann温度分别为(458±20)K(对v″=1)和(447±18)K(对v″=0),得到的CsH分子的转动温度稍低于池温。从转动态分布得到v″=1与v″=0上布居数之比约为0.897,从而计算出CsH基电子态上的平均转动能ER和平均振动能EV,有效能减去平均振转能得到平均平动能ET。CsH分子3种能量的相对比值fT∶fV∶     

Microwave spectrum,dipole moment,and structure of 3-aminopropanol

The microwave spectra of 3-aminopropanol and three of its deuterium substituted isotopic species have been investigated in the 26.5 to 40 GHz frequency region. The rotational spectrum of only one conformer has been assigned in which presumably a hydrogen bond of the OH---N type exists. The rotational spectra of a number of excited vibrational states have been observed and assignments made for some of these excited states. The average intensity ratio for the rotational transitions between the ground and excited vibrational states indicates that the first excited state is about 120 cm^?1 above the ground state.and the next higher state is roughly 200 cm^?1 above the ground vibrational state. The dipole moment was determined from the Stark effect measurements to be 3.13 ± 0.04 D with its principal axes components as |μ_a| = 2.88 ± 0.03 D, |μ_b| = 1.23 ± 0.04 D and |μ_c| = 0.06 ± 0.01 D. The possibility of another conformer where the hydrogen bond could be of NH---O type was explored, but the spectra of such a conformer could not be identified.     

The nu(12) Band of CH(3)SiD(3)

The lowest frequency degenerate fundamental band of CH(3)SiD(3) (v(12) = 1 <-- 0) centered around 418 cm(-1) was measured in order to investigate the vibration-torsion-rotation interactions in a symmetric-top molecule with a single torsional degree of freedom. The spectrum was recorded at an instrumental resolution of 0.004 cm(-1) using a Bomem Fourier transform spectrometer. The temperature and pressure of the sample were 180 K and 2 Torr, respectively. Because of the Coriolis coupling between the torsional stack with one quantum of the silyl rock excited and the corresponding stack for the ground vibrational state, torsional splittings are measured that are substantially larger than expected simply from the observed increase in the barrier height. Due to the local nature of the Coriolis perturbation, the significantly enhanced torsional splittings are confined to a few (K, varsigma) rotational series; here varsigma = -1, 0, 1 labels the torsional sublevels. The current measurements of the nu(12) band and frequencies from previously reported studies in the ground vibrational state were fitted to within experimental uncertainty using an effective Hamiltonian which was used for the analyses of similar spectra in CH(3)SiD(3) and CH(3)CD(3). Spectroscopic parameters characterizing the states v(12) = 0 and 1 and their interactions were determined, including several Coriolis-coupling constants. Copyright 2000 Academic Press.     

Anomalous Vibrational Dependence of the Rotational and Hyperfine Parameters in the B(4)Pi-X(4)Sigma(-) Transition of NbO

The laser excitation spectrum of jet-cooled NbO in the region 16 000-18 000 cm(-1) has been recorded at high resolution, giving rotational and hyperfine constants for the levels v=0-3 of the B(4)Pi state and v=1 of the X(4)Sigma(-) state; zero gaps have also been measured at low resolution for some weaker bands involving higher vibrational levels. Taken together with the laser data for the B-X (0,0) band from Adam et al. (J. Chem. Phys. 94, 6240-6262 (1994)) and the Fourier transform emission data for the doublet manifold from Launila et al. (J. Mol. Spectrosc. 186, 131-143 (1997)), the new data give a very complete picture of the vibrational energy level pattern in this region. Strong irregularities in the vibrational dependences of the B(4)Pi rotational and hyperfine constants can be interpreted in terms of spin-orbit interaction between the B(4)Pi state and the f(2)Pi, e(2)Phi, and d(2)Delta states. The interaction is strong enough that all three doublet states can be seen in absorption from the X(4)Sigma(-) ground state, adding to the complexity of the spectrum. The hitherto unknown sigmadeltasigma* (4)Delta state is estimated to lie near 17 500 cm(-1), from the change of sign in the spin-rotation parameter gamma of the B(4)Pi state between v=2 and 3. Copyright 2001 Academic Press.     

Experimental investigation of ultracold atom-molecule collisions

Ultracold collisions between Cs atoms and Cs2 dimers in the electronic ground state are observed in an optically trapped gas of atoms and molecules. The Cs2 molecules are formed in the triplet ground state by cw photoassociation through the outer well of the 0-(g) (P3/2) excited electronic state. Inelastic atom-molecule collisions converting internal excitation into kinetic energy lead to a loss of Cs2 molecules from the dipole trap. Rate coefficients are determined for collisions involving Cs atoms in either the F=3 or F=4 hyperfine ground state, and Cs2 molecules in either highly vibrationally excited states (nu'=32-47) or in low vibrational states (nu'=4-6) of the a3 summation(u)+ triplet ground state. The rate coefficients beta approximately 10(-10) cm3/s are found to be largely independent of the vibrational and rotational excitation indicating unitary limited cross sections.     

Laser spectroscopy of jet－cooled CuF in visible region

The laser-induced fluorescence excitation spectra of jet-cooled CuF have been recorded in the range of 19000－21470cm^{-1}, in which the CuF radicals were produced by the reaction of SF_6 with copper atoms from a dc discharge-sputtering source under supersonic jet conditions. Eight observed vibronic transition bands have been assigned as the transition from the ground state X(^1Σ^+) to B(^1Σ^+), C(^1Π) and an unreported upper state. The rotational structure of all observed bands has been analysed at the estimated rotational temperature 80K. We determined the newly observed band to be the (^1Π, v=1)－X(^1Σ^+v=0) transition according to the character of the rotational structure and the isotopic shift analysis. In addition, the lifetimes of the states involved in these bands were measured.     

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.     

The Far-Infrared Laser Magnetic Resonance Spectrum of CH2F

Far-infrared laser magnetic resonance (FIR-LMR) spectra due to the CH2F radical have been recorded on seven laser lines at wavelengths between 301 and 568 μm. Observed resonances were assigned to fine and hyperfine components of pure rotational transitions of CH2F in the ground vibrational state and the first excited state of the nu4 out-of-plane bending mode. All assigned transitions obey a-dipole selection rules. The data were combined with previously reported microwave results (Y. Endo, C. Yamada, S. Saito, and E. Hirota, J. Chem. Phys. 79, 1605 (1983)) and subjected to a least-squares fit to determine the parameters of the effective Hamiltonian describing the v4 = 0 and 1 vibrational levels of the CH2F radical. Copyright 1999 Academic Press.     

The millimeter wave spectrum of tertiary butyl fluoride

Rotational spectra of tertiary butyl fluoride (TBF) in the ground and excited vibrational states have been recorded and analyzed. The excited state spectra show large splittings due to l resonance and the effect of the 2, -1 term r_t. Coriolis constants have been obtained for the three lowest degenerate states. An accidental resonance enabled the determination of the axial rotational constant of TBF.     

Millimeter and submillimeter wave rotational spectrum of pyridine in the ground and excited vibrational states

The pure rotational spectra of the ground and five excited vibrational states of pyridine were measured, assigned and fit in the 75-110 and 260-370 GHz frequency bands. An improved set of spectroscopic constants was obtained for the ground state, and all the rotational and quartic centrifugal distortion constants were obtained for the excited vibrational states.     

Millimeter-Wave Spectroscopy of ClBS: An Improved Evaluation of the Equilibrium Structure of Chlorothioborine

The rotational spectrum of the unstable ClBS molecule has been investigated in the millimeter-wave region, from 80 to 195 GHz. A high-temperature reaction between crystalline boron and disulfur dichloride vapor was used to produce the molecule in a flow pyrolysis system. Eight different isotopic species were studied measuring lines in the ground and excited vibrational states 01¹0 (ClBS bend), 10⁰0 (ClB stretch), 02⁰0, 02²0, and 00⁰1 (BS stretch). The analysis of the spectra has been performed taking simultaneously into account both the Fermi resonance between the 10⁰0 and 02⁰0 states, and l-type resonance effects in the v₂=2 vibrational state. This procedure allowed us to calculate directly deperturbed rotational constants, from which the equilibrium rotational constant of seven isotopic variants could be accurately determined yielding a much improved evaluation of the equilibrium structure of chlorothioborine: r_e(ClB)=1.6806±0.0001 Å and r_e(BS)=1.6049±0.0001 Å. The equilibrium structures of ClBS and of the related molecules HBS, FBS, HCP, FCP, and ClCP have been also theo-retically evaluated by high-level CCSD(T) calculations performed using cc-pVTZ, cc-pVQZ, and cc-pV5Z basis sets. The different trends respectively observed for the BS and CP bond lengths in the XBS and XCP triatomic molecules are discussed.     

氨分子在000和201带的选择光离解

本文利用脉冲紫外激光(UV)选择激发氨分子到?¹A″₂电子激发态的两个最低振动能级ν′₂=0和ν′₂=1(ν₂振动),然后检测新生态H原子的飞行谱(TOF),研究了氨分子的光碎片动力学。光谱证实了最近所测的离解能D₀⁰(H-NH₂)=4.645eV;绝大多数生成的NH₂(X²B₁)基处于非振动激发,但是具有围绕a惯性轴的高度转动激发。通过NH₃(?)的ν′₂=1光离解产生的NH₂(X)基具有较高的内部激发,并且显示了在N=K_a转动能级上的反转布居。 关键词：     

激光烧蚀Al热原子与CF4,CCl4,CH2Br2反应中激发态C2的形成

脉冲激光烧蚀平面铝靶产生的热原子与气相CF4,CCl4,CH2Br2的碰撞反应中,在430～600nm之间观测到激发态C2分子的发光光谱,它们可归属为Swan带的d^3Ⅱg=a^3Ⅱu跃迁中△v=2,1,0,-1,-2五个振动序列(v′≤6)。谱强度分析表明,C2激发态可很好的用热平衡描述,其振动温度达6000K左右。同时在△v=0和-1的振动带间观测到振荡的谱峰,它们是转动谱线叠加的结果。激光烧蚀Al产生的等离子体在膨胀中产生的激波及其本身的动能与反应气体碰撞使其解离产生C,然后复合形成C2。C2激发态d可能是通过激发态的Al(^2S)经近共振传能产生,也不排除在有足够碰撞能下优先形成C2激发态b,再通过与d态的v′=6能级交叉无辐射跃迁而进入d态。     

Millimeter-Wave Spectroscopy of HCCCP in Excited Vibrational States

The rotational spectra of the unstable HCCCP molecule have been investigated in the millimeter-wave region for the main excited vibrational states which lie below 1000 cm(-1), namely nu(4) (C&bond;C stretch), nu(5) (HCC bend), nu(6) (CCC bend), nu(7) (CCP bend), 2nu(6), 2nu(7), 3nu(7), 4nu(7), nu(5) + nu(7), and nu(6) + nu(7). l-type resonance effects have been taken into account in the analysis of the spectra, so that the values of the anharmonicity constants x(L(66)), x(L(77)), x(L(57)), and x(L(67)) could be determined. The anharmonic interactions which couple the nu(4) state with nu(6) + nu(7), 2nu(6), and 4nu(7) have been also considered, yielding the unperturbed value of the alpha(4) vibration-rotation coupling constant. Copyright 2001 Academic Press.     

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。     

The Millimeter- and Submillimeter-Wave Spectrum of HC(3)N in the Ground and Vibrationally Excited States

The pure rotational spectrum of the astrophysically very important linear molecule cyanoacetylene, HC(3)N, in the ground and vibrationally excited states has been studied in selected regions from 118 to 814 GHz using the Cologne terahertz spectrometer. Vibrational satellites appendant to the following vibrational states have been recorded and analyzed (v(4), v(5), v(6), v(7)): (0, 0, 0, 1), (0, 0, 0, 2), (0, 0, 1, 0), (0, 0, 1, 1), (1, 0, 0, 0), (1, 0, 0, 1), and the Fermi resonance systems (0, 1, 0, 0)/(0, 0, 0, 3) and (1, 0, 0, 2)/(0, 2, 0, 0)(0e). With the exception of the latter resonance system, all states have been fitted within experimental accuracy. This work provides improved rest frequencies for the astronomical community and may also be beneficial in the improvement of global fits. Copyright 2000 Academic Press.     

The rotation-vibration spectrum and double-minimum ν12 potential function of propadienone: A semirigid bender analysis

Propadienone is an interconverting molecule having a pair of equivalent symmetry related conformers separated by an energy barrier rising well above the vibrational ground state. Microwave spectra of molecules in excited states of the large-amplitude in-plane bending mode ν₁₂, including intersystem lines, have been successfully represented using the semirigid bender model. The model reveals a double-minimum bending potential with a barrier rising 359 cm⁻¹ above the minima at C₁C₂C₃ = 142°. In the ground state the interconversion frequency is 3.7 GHz and the ν₁₂ fundamental frequency is predicted to be 160 cm⁻¹. Analysis of other vibrational satellites involving the lowest-frequency out-of-plane mode ν₈ indicates a vibrational frequency of 240 cm⁻¹. The inplane vibrational satellite and also the ground state substitution spectra are quite accurately reproduced by the model. Our generalized semirigid bender method offers a variety of approaches to fitting molecular parameters to the experimental data.     

The Hyperfine Structures of ScCl and ScF

The Fourier transform microwave spectra of gaseous ScF and ScCl have been measured in their (1)Sigma(+) ground electronic states. Transitions have been observed for ScF (J = 1-0) and for both Sc(35)Cl and Sc(37)Cl (J = 1-0 and J = 2-1) in the ground vibrational state, and for Sc(35)Cl (J = 1-0 and J = 2-1) in the first excited vibrational state. The nuclear quadrupole coupling constants of Sc and of both isotopes of Cl, the spin-rotation constants for all the nuclei and the nuclear spin-nuclear spin constants for both molecules, have been determined. From these hyperfine constants, the electronic structures of ScF and ScCl have been investigated and comparisons have been made to similar molecules. ScCl has been found to be highly ionic. For Sc(35)Cl, the equilibrium bond length has been reevaluated and the vibration frequency and dissociation energy have been estimated. A simple approach to account for the Sc quadrupole coupling constants has been shown to be flawed. Copyright 2000 Academic Press.     

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.