The high resolution rotational spectrum of 2-cyanoaziridine

The microwave spectrum of 2-cyanoaziridine has been measured and assigned. Only the spectrum of the cis isomer has been detected although extensive searches for transitions from the trans isomer have been made, suggesting that it is at least 11 kJ mol^?1 less stable. The following nuclear quadrupole coupling constants were obtained: χ_aa(1) = ?1.249(14), χ_bb(1) = 1.407(12), χ_aa(2) = ?3.547(6), χ_bb(2) = 1.865(8) MHz, the former pair probably referring to the amino nitrogen and the latter pair to the nitrile nitrogen. The rotational constants derived from the analysis are: A = 16877.718(32), B = 3528.931(4), C = 3373.065(4) MHz, D_N = 1.10(4) kHz.     

High resolution laser excitation spectroscopy of barium monosulfide

High-resolution spectra of BaS were recorded using laser excitation spectroscopy. BaS molecules were synthesized in a Broida-type oven. The observed rotationally-resolved spectrum of BaS in the 12 100–12 765 cm^?1 spectral range contains the 2-1, 3-1, 3-2, 4-2, 5-2, 5-3 vibrational bands of the A′¹Π–X¹Σ⁺ transition and the 4-1, 5-1, 5-2 vibrational bands of the a³Π₁–X¹Σ⁺ transition. Approximately 1000 lines of the A′¹Π–X¹Σ⁺ transition and 600 lines of the a³Π₁–X¹Σ⁺ transition for the main isotopologue ¹³⁸Ba³²S (67.5% natural abundance) were measured. Rotational and vibrational parameters were derived for the A′¹Π and a³Π₁ states.     

High resolution laser spectroscopy of Ba Rydberg atoms

The purpose of the present paper is to illustrate some selected aspects of high resolution laser spectroscopy of Rydberg atoms, rather than giving an extensive review of the state of the art. The following topics will be discussed: (i) Excitation and detection of Ba Rydberg atoms with principal quantum numbers up ton≲300; (ii) Stark effect and atomic diamagnetism of high-n Ba Rydberg states in thel-mixing region, (iii) Resonance in singlet-triplet mixing of 6snp¹P₁ and 6snd¹D₂ Ba Rydberg states deduced from hyperfine structure measurements.     

High resolution pulsed cars spectroscopy of the Q-branches of some simple gases

Coherent anti-Stokes Raman spectra of the Q-branches of N₂, O₂ and of v₁ of C₂H₂ have been measured with fairly high resolution (≈ 0.30 cm^-1) by means of a pulsed dye laser system. Calculated CARS spectra show very good agreement with the observed rotational Q-branch structure.     

LiTaO3的高温拉曼光谱研究

利用显微共聚焦拉曼光谱技术研究了LiTaO3晶体在298～948K温度范围内的拉曼光谱,通过对其高波数拉曼峰的分析,研究了LiTaO3的相变机制。研究发现,除466.7cm-1峰外,LiTaO3的其余拉曼峰随着温度的升高向低波数方向明显频移;所有拉曼峰的半高宽随着温度的升高逐渐增加,同时拉曼峰的强度逐渐减弱;在933K附近,LiTaO3的三个拉曼峰的消失,表明LiTaO3发生了从低温铁电相到高温顺电相的相变;与此同时,在该温度附近,359.5,385.0以及466.7cm-1峰的半高宽存在超线性增加。研究结果表明,LiTaO3从低温铁电相到高温顺电相的相变是一种混合型相变,其相变过程可逆。     

The analysis of symmetric rotor Raman spectra: The pure rotational spectrum of 11BF3

The pure rotational Raman spectrum of ¹¹BF₃ has been photographed. Great care was taken in the analysis to consider all the unresolved components under each observed Raman line profile. If this is ignored, systematic errors result. The final set of molecular constants obtained was B₀ = 0.34502(±3 × 10^?5)cm^?1, D_J = 4.38(±0.10) × 10^?7cm^?1, and D_JK = ?9.1(±1.0) × 10^?7cm^?1.     

Raman spectrum and cross sections of n-C3F7I. Implications for a large-scale atomic iodine laser

The Raman spectrum of gaseous n-C₃F₇I has been recorded.Raman cross sections, depolarization ratios, and line widths were measured for the four strongest Raman-active modes. Using the measured values for the 280 cm^-1 mode, the stimulated-Raman gain for a large-scale iodine laser was calculated. The results indicate that losses due to stimulated-Raman scattering will be negligible for a fusion-driver iodine laser.     

High resolution laser induced fluorescence excitation spectroscopy of jet-cooled terrylene

High resolution laser induced fluorescence excitation spectra upon absorption in the A¹B_3u ← X¹A_g band of jet-cooled terrylene have been recorded. Precise energies of three vibronic transitions are deduced. Low lying vibrations are found in both electronic states. Rotational constants in ground and excited state are determined by band contour analysis. Terrylene is a medium-size polycyclic aromatic hydrocarbon (PAH) and a possible carrier of diffuse interstellar bands (DIB). The results of the jet experiments are discussed regarding the PAH-DIB hypothesis.     

High resolution fluorescence spectroscopy by use of a CW dye laser

The hyperfine structure of the Na D₂-line was investigated in a fluorescence experiment involving a narrow band tunable dye laser and a highly collimated atomic beam. The observed linewidth was less than 16 MHz (natural line-width 10 MHz). All hyperfine components were resolved.     

甲苯的激光拉曼光谱研究

采用激光拉曼光谱技术获得了甲苯的振动拉曼光谱,结合群论方法及退偏度测量,指认了其中16条振动谱线,为有机混合物中对甲苯的识别提供了依据。选择甲苯全对称环呼吸振动（1008.8cm-1）为检测谱线,对不同浓度的甲苯/四氯化碳样品进行了分析。研究结果表明：在200.1~2.61g/L浓度范围内,甲苯/四氯化碳振动拉曼光谱强度比与甲苯浓度呈良好的线性关系,线性相关系数为0.997。为甲苯的定量分析提供了一种有效的研究方法。     

High resolution laser spectroscopy of the titanium monohalides, TiCl and TiBr

The electronic spectra of the titanium monohalides, TiCl and TiBr, have been investigated in the blue-violet region using a laser ablation molecular beam spectrometer. Five subbands assigned as ⁴Γ_5/2-X⁴Φ_3/2 (0, 0), ⁴Γ_5/2-X⁴Φ_3/2 (1, 1), ⁴Γ_5/2-X⁴Φ_5/2 (0, 0), ⁴Γ_7/2-X⁴Φ_5/2 (0, 0) and ⁴Γ_7/2-X⁴Φ_7/2 (0, 0) were observed and recorded at both low and high-resolution for titanium monochloride. A Hund’s case (a) rotational analysis has been carried out for the ⁴⁸Ti³⁷Cl and ⁴⁸Ti³⁵Cl isotopic species, and polynomial analyses for these, as well as the ⁴⁶Ti³⁵Cl, ⁴⁷Ti³⁵Cl, ⁴⁹Ti³⁵Cl, and ⁵⁰Ti³⁵Cl isotopologues have been completed. The same spectral region yielded several molecular transitions for titanium monobromide, 10 of which were recorded at high resolution. Six of these have been attributed to a ⁴Γ-X⁴Φ electronic transition at 23 484 cm⁻¹, while the remaining four have been assigned to a second ⁴Γ-X⁴Φ electronic transition at 23 613 cm⁻¹. A Hund’s case (a) global analysis has been carried out for the ⁴⁸Ti⁷⁹Br and ⁴⁸Ti⁸¹Br isotopologues.     

甲苯的激光拉曼光谱研究

采用激光拉曼光谱技术获得了甲苯的振动拉曼光谱,结合群论方法及退偏度测量,指认了其中16条振动谱线,为有机混合物中对甲苯的识别提供了依据．选择甲苯全对称环呼吸振动（1008.8cm－1）为检测谱线,对不同浓度的甲苯／四氯化碳样品进行了分析．研究结果表明：在200．1～2．61g／L浓度范围内,甲苯／四氯化碳振动拉曼光谱强度比与甲苯浓度呈良好的线性关系,线性相关系数为0.997．为甲苯的定量分析提供了一种有效的研究方法．     

The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave spectroscopy

The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy is presented. A new CP-FTMW spectrometer capable of measuring the entire 7.5-18.5 GHz spectrum with a single polarizing pulse is described briefly. The CP-FTMW spectrometer takes advantage of recent advances in digital electronics by utilizing a 4.2 GS/s arbitrary waveform generator as a frequency source and a 12 GHz digital oscilloscope to digitize the down converted molecular free induction decay (FID). Signal averaging in the time domain is used to increase the signal-to-noise ratio. The rotational constants of three unique conformers of epifluorohydrin were measured, as well as the rotational constants of the three unique ¹³C isotopomers and the ¹⁸O isotopomer (in natural abundance) of the most stable conformer. The rotational constants of the two less stable conformers differ significantly from those previously reported [F.G. Fujiwara, J.L. Painter, H. Kim, J. Mol. Struct. 41 (1977) 169-175]. Ab initio calculations were performed for all three conformations and are compared to experimental values.     

Limiting temporal and spectral resolution in spectroscopy and microscopy of coherent Raman scattering with chirped ultrashort laser pulses

Chirped ultrashort light pulses offer new options for coherent nonlinear spectroscopy and microscopy. We show here that the temporal resolution of spectroscopy and microscopy based on coherent anti-Stokes Raman scattering (CARS) can be smoothly tuned within a broad range, with upper and lower bounds of this range controlled by the pump and probe pulse durations. The spectral resolution of CARS spectroscopy and microscopy is analyzed as a function of the duration and chirp of the pump pulses. Pulses with a periodic phase modulation can provide the limiting spectral resolution of the CARS technique, corresponding to the lower bound of uncertainty in spectral measurements, dictated by the uncertainty principle.     

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.