The absorption spectrum of phosphine (PH3) between 2.8 and 3.7 μm: Line positions, intensities, and assignments

Over 8000 line positions and intensities of phosphine (PH₃) at 3 μm have been measured at 0.0115 cm⁻¹ resolution with the McMath-Pierce Fourier Transform spectrometer at Kitt Peak. The observed line intensities ranged from 4.13 × 10⁻⁶ to 4.69 × 10⁻² cm⁻² atm⁻¹ at 296 K, for line positions between 2724.477 and 3601.652 cm⁻¹. This region spans eight interacting vibrational states: 3ν₂ (2940.8 cm⁻¹), 2ν₂ + ν₄ (3085.6 cm⁻¹), ν₂ + 2ν₄ (3214.9 cm⁻¹), ν₁ + ν₂ (3307.6 cm⁻¹), ν₂ + ν₃ (3310.5 cm⁻¹), 3ν₄ (∼3345 cm⁻¹), ν₁ + ν₄ (3426.9 cm⁻¹), and ν₃ + ν₄ (3432.9 cm⁻¹). Assignments have been determined for all the bands except 3ν₄ (a weak band in a highly congested area) for a total of 4232 transitions. The total integrated intensity for this region is 5.70 cm⁻² atm⁻¹ near 296 K, and assigned lines account for 79% of the observed absorption. The two strongest bands in the region are ν₁ + ν₄ and ν₃ + ν₄ with band strengths at 296 K of 1.61 and 2.01 cm⁻² atm⁻¹, respectively. An empirical database of PH₃ line parameters (positions, intensities, and assignments) is now available. Lower state energies (corresponding to assignments from this study) and line widths from the literature are included; default values are used for unassigned features.     

Vibrational and Rotational Spectroscopy of 13CD3OD

We have used Fourier Transform spectral data on the C-O stretching mode of ¹³CD₃OD in order to perform a vibro-rotational analysis for this molecule. We have estimated a few molecular parameters of the ground and C-O stretching vibrational modes. Based on these parameters, and by using the Kwan-Dennison model, we propose assignments for a number of far-infrared laser transitions of ¹³CD₃OD.     

Infrared optical constants, dielectric constants, molar polarizabilities, transition moments, dipole moment derivatives and Raman spectrum of liquid cyclohexane

Previous studies have been done in this laboratory focusing on the optical properties of several liquid aromatic and aliphatic hydrocarbons in the infrared. The current study reports the infrared and absorption Raman spectra of liquid cyclohexane. Infrared spectra were recorded at 25 °C over a wavenumber range of 7400–490 cm⁻¹. Infrared measurements were taken using transmission cells with pathlengths ranging from 3 to 5000 μm. Raman spectra were recorded between 3700 and 100 cm⁻¹ at 25 °C using a 180° reflection geometry. Ab initio calculations of the vibrational wavenumbers at the B3LYP/6311G level of theory were performed and used to help assign the observed IR and Raman spectra. Extensive assignments of the fundamentals and binary combinations observed in the infrared imaginary molar polarizability spectrum are reported. The imaginary molar polarizability spectrum was curve fitted to separate the intensity from the various transitions and used to determine the transition moments and magnitudes of the derivatives of the dipole moment with respect to the normal coordinates for the fundamentals.     

A computer assisted procedure of assignments of vibration–rotation bands of asymmetric and symmetric top molecules

An advanced graphically oriented interactive program package for assignments of complex (perturbed) vibration–rotation spectra of asymmetric and symmetric top molecules has been developed. In addition to the well known Loomis–Wood algorithm, the new procedure takes advantage of a precise knowledge of the lower (e.g. ground) vibrational state energies, works with a realistic approximation of effective Hamiltonians for lower as well as upper vibrational states, and allows an instant combination difference inspection of spectral lines by the graphical representation of the appropriate parts of the analyzed experimental spectrum. Being constrained to the combination difference checking, the new algorithm can directly assign the correct rotational quantum numbers as well as ‘quality weights’ estimating relative accuracies of the identified lines.     

Advanced graphical software for assignments of transitions in rovibrational spectra

We have developed advanced graphical software for significantly accelerated and verified assignments of rotationally resolved rovibrational molecular spectra. The program combines the traditional approach of Loomis-Wood diagrams, which are used to visualize spectral branches and facilitate their identification, with the power of interactive combination difference checking, which provides an immediate verification of correct assignments of quantum numbers to spectral lines. Assignment procedures and other tools of the program are designed in a fully graphical Windows environment to accelerate the usually tedious assignment work and make the use of the program highly intuitive. The use of an appropriate rovibrational Hamiltonian for fitting the assigned transitions is made easy by the flexible, user-programmed interfaces for exporting assigned data directly in the needed format and importing rovibrational energies back to the assignment program. The program is designed for the MS Windows operating systems and is available upon request with a full documentation on http://www.lww.amu.edu.pl.     

1H AND 13C NMR Assignments of Artheethers

The ¹H and ¹³C nmr assignments for all hydrogen and carbon atoms were made for β and α arteethers (5 and 6) based on chemical shift theory and 2D-nmr techniques (COSY and HETCOR).     

A reevaluation of the assignment of the vibrational fundamentals and the rotational analysis of bands in the high-resolution infrared spectra of trans- and cis-1,3,5-hexatriene

Assignments of the vibrational fundamentals of cis- and trans-1,3,5-hexatriene are reevaluated with new infrared and Raman spectra and with quantum chemical predictions of intensities and anharmonic frequencies. The rotational structure is analyzed in the high-resolution (0.0013-0.0018 cm⁻¹) infrared spectra of three C-type bands of the trans isomer and two C-type bands of the cis isomer. The bands for the trans isomer are at 1010.96 cm⁻¹ (ν₁₄), 900.908 cm⁻¹ (ν₁₆), and 683.46 cm⁻¹ (ν₁₇). Ground state (GS) rotational constants have been fitted to the combined ground state combination differences (GSCDs) for the three bands of the trans isomer. The bands for the cis isomer are at 907.70 cm⁻¹ (ν₃₃) and 587.89 cm⁻¹ (ν₃₅). GS rotational constants have been fitted to the combined GSCDs for the two bands of the cis isomer and compared with those obtained from microwave spectroscopy. Small inertial defects in the GSs confirm that both molecules are planar. Upper state rotational constants were fitted for all five bands.     

A general assignment method for oriented sample (OS) solid-state NMR of proteins based on the correlation of resonances through heteronuclear dipolar couplings in samples aligned parallel and perpendicular to the magnetic field

The acquisition and different appearances observed for wide bandwidth solid-state MAS NMR spectra of low-γ nuclei, using (14)N as an illustrative nucleus and employing two different commercial spectrometers (Varian, 14.1T and Bruker, 19.6T), have been compared/evaluated and optimized from an experimental NMR and an electronic engineering point of view, to account for the huge differences in these spectra. The large differences in their spectral appearances, employing the recommended/standard experimental set-up for the two different spectrometers, are shown to be associated with quite large differences in the electronic design of the two types of preamplifiers, which are connected to their respective probes through a 50Ω cable, and are here completely accounted for. This has led to different opportunities for optimum performances in the acquisition of nearly ideal wide bandwidth spectra for low-γ nuclei on the two spectrometers by careful evaluation of the length for the 50Ω probe-to-preamp cable for the Varian system and appropriate changes to the bandwidth (Q) of the NMR probe used on the Bruker spectrometer. Earlier, we reported quite distorted spectra obtained with Varian Unity INOVA spectrometers (at 11.4 and 14.1T) in several exploratory wide bandwidth (14)N MAS NMR studies of inorganic nitrates and amino acids. These spectra have now been compared/evaluated with fully analyzed (14)N MAS spectra correspondingly acquired at 19.6T on a Bruker spectrometer. It is shown that our upgraded version of the STARS simulation/iterative-fitting software is capable of providing identical sets for the molecular spectral parameters and corresponding fits to the experimental spectra, which fully agree with the electronic measurements, despite the highly different appearances for the MAS NMR spectra acquired on the Varian and Bruker spectrometers.     

Infrared and far-infrared spectroscopy of CH3OH: TeraHertz laser lines and assignments

We use a ¹³CO₂ laser as optical pumping source to search for new THz laser lines generated from ¹³CH₃OH. Nineteen new THz laser lines (also identified as far-infrared, FIR) ranging from 42.3 μm (7.1 THz) to 717.7 μm (0.42 THz) are reported. They are characterized in wavelength, offset, relative polarization, relative intensity, and optimum working pressure. We have assigned eight laser lines to specific rotational energy levels in the excited state associated with the C-O stretching mode.     

基于拉曼光谱实验与密度泛函理论的宝石级红珊瑚拉曼谱峰归属研究

红珊瑚是一种珍贵的有机宝石,自古以来因其红润的颜色与细腻的质地深受人们的喜爱与追捧。颜色漂亮的天然红珊瑚产量稀少,故有些红珊瑚会经过染色处理来改善其外观。拉曼光谱测试是鉴定红珊瑚有无经过染色处理的有力手段,故红珊瑚拉曼谱峰的归属对于鉴定有着重要的理论指导意义。由于红珊瑚拉曼峰的归属问题一直没有被深入研究,基于此,该研究测试了三颗颜色深浅不同的红珊瑚（Corallium rubrum）的拉曼光谱。同时,使用量子化学程序Gaussian 16运用密度泛函理论计算了红珊瑚中色素分子角黄素的理论拉曼光谱。创新性对比红珊瑚的实验拉曼光谱与角黄素分子的理论拉曼光谱,并进一步分析红珊瑚拉曼峰的归属。结果发现,红珊瑚的拉曼光谱中主要有1 514,1 295,1 177,1 125,1 086和1 016 cm-1拉曼峰,其中1 086 cm-1处的拉曼峰是方解石的CO2-₃引起的。红珊瑚的红色越深,1 514,1 295,1 177,1 125和1 016 cm-1拉曼峰的强度越强,反之,红珊瑚的红色越浅,这些拉曼峰的强度越弱。红珊瑚拉曼光谱中的1 514,1 295,1 177,1 125和1 016 cm-1峰强与红珊瑚的红色深浅呈现出正相关的关系,故推测这套拉曼峰是由红珊瑚中的色素产生的。角黄素理论拉曼光谱中主要存在的拉曼峰位于1 512,1 269,1 189,1 159和999 cm-1处,与红珊瑚实验拉曼光谱中的1 514,1 295,1 177,1 125和1 016 cm-1峰的形状位置高度吻合。振动分析结果表明,角黄素的1 512,1 269,1 189,1 159和999 cm-1拉曼峰分别是由CC伸缩振动,C-H摇摆振动,C-C伸缩振动,C-C伸缩振动与甲基摇摆振动引起的。因此将红珊瑚拉曼光谱中的1 514,1 295,1 177,1 125和1 016 cm-1峰归属为CC伸缩振动,C-H摇摆振动,C-C伸缩振动,C-C伸缩振动与甲基摇摆振动。使用密度泛函理论的计算方法研究了红珊瑚拉曼谱峰的归属并对红珊瑚的拉曼谱峰进行了指认,为使用拉曼光谱鉴定红珊瑚提供了理论基础。同时为研究这类生物宝石材料拉曼谱峰的归属提供了一种新的方法。