Assignment and analysis of the rotational spectrum of bromoform enabled by broadband FTMW spectroscopy

The rotational spectrum of the bromoform molecule is complicated by overlap of extensive hyperfine splitting structure of three bromine nuclei belonging to four isotopic species of comparable abundance. We have been able to achieve an unambiguous assignment of this spectrum on the basis of complete hyperfine patterns of the lowest-J rotational transitions recorded at conditions of supersonic expansion with chirped-pulse, broadband Fourier transform microwave spectroscopy. The mm-wave rotational spectrum was then also studied up to J = 131 and 318 GHz, and extensive measurements are reported for four isotopic species of HCBr₃ and four DCBr₃ species. Precise values of many spectroscopic constants have been determined from global fits of all measurements for a given isotopic species and have been substantiated by comparisons among the various isotopic species and with results of ab initio calculations. The experimental measurements allowed determination of the axial rotational constant C for the symmetric top species, evaluation of nuclear quadrupole hyperfine splitting constants in the principal quadrupole axes of the bromine nucleus, and extension of the range of known values of the h₃ splitting constant. The r_z geometry of HCBr₃ was also determined.     

Rotational spectrum of C chloromethanes

Rotational spectra of 13 carbon chloromethane isotopologues ¹³CH₃³⁵Cl and ¹³CH₃³⁷Cl with resolved hyperfine structures were measured in the spectral region from 50 GHz to 275 GHz. An estimated uncertainty of individual well developed lines was better than 5 kHz. Ground state molecular parameters B, D_J, D_JK, H_J, H_JK, H_KJ, eQq, and C_N were derived. Determination mainly of the hyperfine constants is significantly better than in previous studies.     

Rotational spectrum of trifluoroacetone

The rotational spectra of 5 isotopologues of 1,1,1-trifluoroacetone have been assigned using pulsed-jet Fourier-transform microwave spectroscopy. All rotational transitions appear as doublets, due to the internal rotation of the methyl group. Analysis of the tunneling splittings using both the principal axis method (PAM) and the combined axis method (CAM) methods allows to determine accurately the height of the threefold barrier to internal rotation of the methyl group, and its orientation, leading to V₃ = 3.28 and 3.10 kJ mol⁻¹, respectively. The r_s geometry of the molecular skeleton, a partial r₀ structure of the molecule and supporting ab initio calculations are also reported.     

钕离子同位素移位和超精细结构光谱

原子光谱中,同位素移位和超精细结构光谱是少数几个能够将原子物理和原子核物理这两个不同的物理分支联系起来的课题之一.利用共线快离子束-激光光谱学方法测量了单电荷态钕离子4f45d6G3/2→(26041)°5/2跃迁(波长577.21 nm)的共振光谱,得到了所有7个稳定同位素(A=142～146,148,150)之间的能量移位和2个奇同位素(A=143,145)的超精细结构光谱.     

The magnetic hyperfine structure in the rotational spectrum of H2CNH

The hyperfine structure in the ground-state rotational spectrum of methanimine was studied in the frequency range of 64-172 GHz by means of the Lamb-dip technique. This allowed to resolve, in some hyperfine components due to the ¹⁴N nucleus, doublets separated by only some tenth of kHz. We explain the splittings as due to magnetic interactions of the three protons with their molecular environment. The analysis of the experimental spectrum has been guided by quantum-chemical calculations of the hyperfine parameters.     

Millimeter-wave spectrum of BrCN produced by dc discharge

Ground state (v=0) and first excited state (v=1) millimeter-wave rotational absorption spectra of cyanogen bromide (BrCN) and some of its isotopic species, have been investigated in the frequency region: 40.0-75.0 GHz using a source-modulated millimeter-wave spectrometer. Millimeter-wave radiation has been produced using a frequency multiplier, the fundamental radiation source being klystrons. BrCN has been produced by applying a dc glow discharge through a mixture of 3-bromobenzonitrile and trifluoromethylbromide (CF₃Br) at low pressure. The quadrupole hyperfine structure of ⁸¹Br and ⁷⁹Br have been resolved, measured, and analyzed. Finally, internuclear distances of BrCN have been determined.     

Rotational Spectrum of CBr by Kinetic Microwave Spectroscopy of 193-nm Photolysis Products of Bromoform

We have measured the first millimeter-wave spectrum of CBr. The radical was produced by pulsed UV-laser photolysis of bromoform at 193 nm and detected using kinetic spectroscopy. We have significantly improved the rotational and fine structure constants for the ground vibrational state. The hyperfine structure due to the bromine nucleus has been resolved and quadrupole and magnetic hyperfine parameters evaluated for the first time. Copyright 2000 Academic Press.     

The Lamb-dip spectrum of methylcyanide: Precise rotational transition frequencies and improved ground-state rotational parameters

Methylcyanide, CH₃CN, is an important interstellar species, and therefore the accurate knowledge of precise rest frequencies for rotational transitions as well as ground-state rotational and hyperfine constants is needed. In this work the hyperfine structure of the millimeter- and submillimeter-wave spectra of CH₃CN has been further investigated. In addition, accurate THz measurements have been carried out for the first time. Consequently, the present investigation allowed us to provide the most accurate ground state rotational and hyperfine parameters known at the moment for CH₃C¹⁴N. To resolve the hyperfine structure of the rotational transitions observed, the Lamb-dip technique has been exploited. Both frequency-modulated and video-type detections have been employed.     

~(141)Pr~ 581.69nm谱线超精细结构光谱研究

利用共线快离子束 激光光谱学方法测量了正一价镨离子波长 5 81.6 9nm谱线的超精细结构光谱 ,得到了超精细相互作用常数 ;与已发表的数据比较 ,在测量误差范围内一致 ,我们的测量精度提高了一个量级     

The pure rotational spectrum of ZnCl (XΣ): Variations in zinc halide bonding

The radical ZnCl (X²Σ⁺) has been studied using millimeter-wave direct-absorption techniques. Pure rotational spectra of ⁶⁷Zn³⁵Cl, ⁶⁶Zn³⁷Cl, ⁶⁸Zn³⁵Cl, ⁶⁴Zn³⁵Cl, ⁶⁴Zn³⁷Cl, and ⁶⁶Zn³⁵Cl were measured in the vibrational ground state and data were also recorded for the latter three in the v = 1 and v = 2 states. Every rotational transition was found to be split into a doublet due to spin-rotation interactions. For ⁶⁷Zn³⁵Cl, each doublet exhibited additional splittings arising from hyperfine coupling of the ⁶⁷Zn (I = 5/2) nucleus. Rotational, fine structure, and hyperfine constants have been determined from these data, and equilibrium parameters calculated. The equilibrium bond length of ⁶⁴Zn³⁵Cl is found to be 2.13003305(24) Å, in good agreement with recent theoretical predictions. Interpretation of hyperfine constants indicates that the 12σ orbital is ∼70% Zn(4s) in character, suggesting that the zinc chloride bond is relatively ionic.     

The Lamb-dip spectrum of phosphine: The nuclear hyperfine structure due to hydrogen and phosphorus

For the first time, the hyperfine structure of the rotational J = 1 ← 0 (K = 0) and J = 2 ← 1 (K = 0, 1) transitions of phosphine has been resolved by using microwave spectroscopy. To this purpose, the Lamb-dip technique has been employed. In addition, the J = 3 ← 2 (K = 0, 1, 2) transition has been recorded at Doppler resolution. The present investigation allowed us to provide accurate values for most of the hyperfine constants as well as ground state rotational parameters.     

Research of cornea section''s shape ablated by 193-nm ArF laser spots

The ablation theory of cornea and biology effect by 193-nm ArF excimer laser are introduced. The ablation tracks model is put forward to make laser spots scan around cornea by many steps and many areas to change cornea curvature. The corneal average ablation curve is calculated by software so as to explain the feasibility of the ablation tracks model. By analyzing the actual ablation shapes of many arbitrary cornea sections, the optimal ablation method for deciding the random position of every laser spot in every ablation track is obtained. Experiments combining the ablation model with the device testify the energy stability of laser spots and the accuracy of rectifying anisometropia.     

Microwave spectrum of isotopic species of urea (NH2)2CO

We report new microwave measurements for the (¹⁵NH₂)₂CO and (¹⁴NH₂) (¹⁵NH₂)CO isotopologues of urea. The spectra were recorded between 5 and 20 GHz with our MWFT spectrometer coupled to a newly built heated nozzle. A new centrifugal distortion analysis was performed for the (¹⁵NH₂)₂CO species including all available data. For the (¹⁴NH₂) (¹⁵NH₂)CO species the hyperfine structure was recorded for the first time.     

Millimeter and submillimeter wave spectroscopic investigations into the rotation-tunneling spectrum of gGg ethylene glycol, HOCH2CH2OH

The rotation-tunneling spectrum of the second most stable gGg^′ conformer of ethylene glycol (1,2-ethanediol) in its ground vibrational state has been studied in selected regions between 77 and 579 GHz. Compared to the study of the more stable aGg^′ conformer, a much larger frequency range was studied, resulting in a much extended frequency list covering similar quantum numbers, J?55 and K_a?19. While the input data were reproduced within experimental uncertainties up to moderately high values of J and K_a larger residuals remain at higher quantum numbers. The severe mixing of the states caused by the Coriolis interaction between the two tunneling substates is suggested to provide a considerable part of the explanation. In addition, a Coriolis interaction of the gGg^′ ground vibrational state with an excited state of the aGg^′ conformer may also contribute. Relative intensities of closely spaced lines have been investigated to determine the signs of the Coriolis constants between the two tunneling substates relative to the dipole moment components and to estimate the magnitudes of the dipole moment components and the energy difference between the gGg^′ and the aGg^′ conformers. Results of ab initio calculations on the total dipole moment and the vibrational spectrum were needed for these estimates. The current analysis is limited to transitions with quantum numbers J?40 and K_a?6 plus those having J?22 and K_a?17 which could be reproduced within experimental uncertainties. The results are aimed at aiding radioastronomers to search for gGg^′ ethylene glycol in comets and in interstellar space.     

High resolution rotational spectrum of FCO2 radical (extension to lower frequencies)

We have subsequently extended the measurement of the FC¹⁶O₂ radical to the lower frequency region, between 210 and 245 GHz with the recently developed Prague microwave spectrometer. About 60 new a-type R-branch transitions have been observed. Our present analysis enabled us to improve significantly the determination of the ground state constants: most of the parameters are now determined with higher precision up to an order of magnitude better than the previous study. In addition eight new constants could be determined or nearly determinable for the first time.     

Rotational distribution of nascent OH radicals after H2O2 photolysis at 193 nm

The rotational distribution of OH(X ²,v=0) radicals was investigated by resonant laser-induced fluorescence (LIF) after photolysis of H₂O₂ at 193 nm. A microcomputer equipped LIF arrangement allowed special shot-by-shot normalization of the fluorescence signal for noise reduction. Using a least-squares procedure we were able to account for all measured line intensities including overlapping lines (blends) and obtain a complete rotational state distribution of the OH(X ²,v=0) state. The rotational excitation shows a Gaussian-like distribution with a maximum atK=12 and with 16% of the total available energy (17,400 cm^–1) appearing in rotation. Only 1% of the available energy is converted into vibration, leaving over 83% for translational excitation. The measured rotational distribution appears to fit a semiclassical theory.     

Analysis of the spectral structure of CuBr laser lines

The spectral structure of spontaneous emission of copper atom at 510.6 nm and 578.2 nm was calculated considering the hyperfine structure of energy levels and the isotope shift. The spectral structure of the 510.6 nm and 578.2 nm laser lines was measured in a sealed-off CuBr laser tube with periodic refreshment of the neon buffer gas under different work temperature and excited voltage. The spectral structure of the spontaneous emission of copper atom was found to have similar outline with its laser lines. The spectrum of the 510.6 nm laser line maintains similar outline with three peaks at various discharging parameters while the spectrum of the 578.2 nm laser line is strongly dependent on the reservoir temperature and the discharge voltage.     

Sn and Sn hyperfine structure in the rotational spectrum of tin monosulfide recorded using laser ablation-source equipped, chirped-pulse Fourier transform microwave spectroscopy

Tin metal has been ablated with pulsed radiation from a Nd:YAG laser (λ=1064 nm). Carbonyl sulfide, diluted in high pressure argon, has been pulsed into the resultant Sn plasma. One of the results of this experiment has been the production of SnS. These events have allowed a rotational spectrum of tin monosulfide to be studied using a chirped-pulse Fourier transform microwave spectrometer. The resolution of the spectrum obtained was sufficient to observe hyperfine structure from the ¹¹⁷Sn and ¹¹⁹Sn-containing SnS molecules. Tin nuclear spin-rotation hyperfine constants are reported for the first time.     

Microwave spectrum of C methyl iodide

The results of reinvestigation of millimeter and submillimeter-wave spectrum of ¹³CH₃I molecule are reported. Microwave spectrum records were carried out in the frequency range 50-250 GHz and 280-330 GHz. For several series of rotational transitions the accuracy of measurements was improved by an order of magnitude. On the basis of large amount of experimental data (about 800 rotational transitions) for the first time the most complete set of molecular constants was obtained. Also for most of parameters the estimation accuracies were improved by several orders of magnitude.     

Ground state spectrum of methylcyanide

The rotational spectrum of methylcyanide (acetonitrile) in the ground vibrational state was measured in the spectral region from 91 to 810 GHz using the Cologne and Tsukuba spectrometers operated in the Doppler-limited and sub-Doppler saturation layouts. The resolution of the saturation Lamb-dip measurements is estimated to be about 1 kHz at the best of circumstances and the measuring accuracy of 10-60 kHz depending very sensitively on the quality of the spectrum. In the cases of rotational transitions with the low quantum number J (J<18) and with a low difference of the rotational quantum numbers J−K, the resolved or partly resolved hyperfine structures of the rotational transitions were observed. Together with the most accurate data from the literature, the newly measured experimental data were analyzed using the traditional polynomial energy formula as well as the Padè approximant for the effective rotational Hamiltonian. The resulting rotational, centrifugal distortion, and hyperfine structure spectroscopic constants were obtained with a significantly higher accuracy than the ones listed in the literature. In addition, an anomalous accidental resonance was detected between the K=14 ground state levels and the K=12, +l levels in the excited v₈=1 vibrational state.