Vibration-rotation Transitions Research Articles

Derivation of gravity wave intrinsic parameters and vertical wavelength using a single scanning OH(3-1) airglow spectrometer

Abstract. For the first time, we present an approach to derive zonal, meridional, and vertical wavelengths as well as periods of gravity waves based on only one OH* spectrometer, addressing one vibrational-rotational transition. Knowledge of these parameters is a precondition for the calculation of further information, such as the wave group velocity vector. OH(3-1) spectrometer measurements allow the analysis of gravity wave ground-based periods but spatial information cannot necessarily be deduced. We use a scanning spectrometer and harmonic analysis to derive horizontal wavelengths at the mesopause altitude above Oberpfaffenhofen (48.09∘ N, 11.28∘ E), Germany for 22 nights in 2015. Based on the approximation of the dispersion relation for gravity waves of low and medium frequencies and additional horizontal wind information, we calculate vertical wavelengths. The mesopause wind measurements nearest to Oberpfaffenhofen are conducted at Collm (51.30∘ N, 13.02∘ E), Germany, ca. 380 km northeast of Oberpfaffenhofen, by a meteor radar. In order to compare our results, vertical temperature profiles of TIMED-SABER (thermosphere ionosphere mesosphere energetics dynamics, sounding of the atmosphere using broadband emission radiometry) overpasses are analysed with respect to the dominating vertical wavelength.

First Laboratory Detection of Vibration-Rotation Transitions of 12CH+ and 13CH+ and Improved Measurement of their Rotational Transition Frequencies.

The long-searched C-H stretches of the fundamental ions CH+ and 13CH+ have been observed for the first time in the laboratory. For this, the state-dependent attachment of He atoms to these ions at cryogenic temperatures has been exploited to obtain high-resolution rovibrational data. In addition, the lowest rotational transitions of CH+, 13CH+ and CD+ have been revisited and their rest frequency values improved substantially.

Critical evaluation of measured rotational–vibrational transitions of four sulphur isotopologues of S16O2

A critical evaluation and validation of the complete set of previously published experimental rotational–vibrational line positions is reported for the four stable sulphur isotopologues of the semirigid SO2 molecule – i.e., 32S16O2, 33S16O2, 34S16O2, and 36S16O2. The experimentally measured, assigned, and labeled transitions are collated from 43 sources. The 32S16O2, 33S16O2, 34S16O2, and 36S16O2 datasets contain 40,269, 15,628, 31,080, and 31 lines, respectively. Of the datasets collated, only the extremely limited 36S16O2 dataset is not subjected to a detailed analysis. As part of a detailed analysis of the experimental spectroscopic networks corresponding to the ground electronic states of the 32S16O2, 33S16O2, and 34S16O2 isotopologues, the MARVEL (Measured Active Rotational–Vibrational Energy Levels) procedure is used to determine the rovibrational energy levels. The rovibrational levels and their vibrational parent and asymmetric-top quantum numbers are compared to ones obtained from accurate variational nuclear-motion computations as well as to results of carefully designed effective Hamiltonian models. The rovibrational energy levels of the three isotopologues having the same labels are also compared against each other to ensure self-consistency. This careful, multifaceted analysis gives rise to 15,130, 5852, and 10,893 validated rovibrational energy levels, with a typical accuracy of a few 0.0001 cm−1, for 32S16O2, 33S16O2, and 34S16O2, respectively. The extensive list of validated experimental lines and empirical (MARVEL) energy levels of the S16O2 isotopologues studied are deposited in the Supplementary Material of this article, as well as in the distributed information system ReSpecTh (http://respecth.hu).

Planar Spontaneous Raman-Scattering Spectroscopy for Reacting Jet-Flow Diagnostics Using Lyot–Ehman Tunable Filter

The spatial-density distribution in burning a premixed methane–air swirling turbulent jet has been studied by measuring the intensity of the Stokes branch of spontaneous Raman scattering for vibrational–rotational transitions in nitrogen. An optical system comprising a Nd:YAG laser and the liquid-crystalline Lyot–Ehman tunable filter has been created and tested by measuring the temperature and density fields in a cone-shaped laminar flame. It has been established that the difference of data obtained using the Stokes component of Raman scattering in nitrogen and its ratio to the anti-Stokes component does not exceed 5% in a temperature range from 300 to 1800 K.

Панорамная спектроскопия спонтанного комбинационного рассеяния для диагностики струйных реагирующих потоков с использованием перестраиваемого фильтра Лио-Эмана

AbstractThe spatial-density distribution in burning a premixed methane–air swirling turbulent jet has been studied by measuring the intensity of the Stokes branch of spontaneous Raman scattering for vibrational–rotational transitions in nitrogen. An optical system comprising a Nd:YAG laser and the liquid-crystalline Lyot–Ehman tunable filter has been created and tested by measuring the temperature and density fields in a cone-shaped laminar flame. It has been established that the difference of data obtained using the Stokes component of Raman scattering in nitrogen and its ratio to the anti-Stokes component does not exceed 5% in a temperature range from 300 to 1800 K.

Ultra-sensitive probe of spectral line structure and detection of isotopic oxygen

We discuss a new method of investigating and obtaining quantitative behavior of higher harmonic (> 2f) wavelength modulation spectroscopy (WMS) based on the signal structure. It is shown that the spectral structure of higher harmonic WMS signals, quantified by the number of zero crossings and turnings points, can have increased sensitivity to ambient conditions or line-broadening effects from changes in temperature, pressure, or optical depth. The structure of WMS signals, characterized by combinations of signal magnitude and spectral locations of turning points and zero crossings, provides a unique scale that quantifies lineshape parameters and, thus, useful in optimization of measurements obtained from multi-harmonic WMS signals. We demonstrate this by detecting weaker rotational–vibrational transitions of isotopic atmospheric oxygen (16O18O) in the near-infrared region where higher harmonic WMS signals are more sensitive contrary to their signal-to-noise ratio considerations. The proposed approach based on spectral structure provides the ability to investigate and quantify signals not only at linecenter but also in the wing region of the absorption profile. This formulation is particularly useful in tunable diode laser spectroscopy and ultra-precision laser-based sensors where absorption signal profile carries information of quantities of interest, e.g., concentration, velocity, or gas collision dynamics, etc.

Water-molecular emission from cavitation bubbles affected by electric fields

Orange emission was observed during multibubble sonoluminescence at 1 MHz in water saturated with noble gas. The emission arose in the vicinity of the peeled ground electrode of a piezoceramic transducer exposed to water, suggesting that cavitation bubbles were affected by the electric fields that leaked from the transducer. The spectrum of the emission exhibited a broad component whose intensity increased towards the near-infrared region with peaks at 713 and 813 nm. The spectral shape was independent of the saturation gas of He, Ne, or Kr. The broad component was attributed to the superposition of lines due to vibration-rotation transitions of water molecules, each of which was broadened by the high pressure and electric fields at bubble collapse. An emission mechanism based on charge induction by electric fields and the charged droplet model is proposed.

Spectral characteristics of Q-switched CO laser

The spectrum of low-pressure cryogenic CO laser operated in Q-switched mode was measured at frequencies of 70 Hz and 120 Hz. CO laser spectrum consisted of 115 spectral lines in the wavelength range from 4.89 μm to 6.54 μm at 70 Hz, and 102 lines in the wavelength range from 4.90 μm to 6.44 μm at 120 Hz. For the first time the dynamics of generation on each spectral line for full CO laser spectrum were measured. We identified rotational-vibrational transitions and analyzed the processes, which affect the formation of the CO laser spectrum. This data were taken into account to determine the peak powers of all the spectral lines correctly.

High resolution FTIR spectroscopy of the ν7 band of CD3CCH

The high-resolution Fourier transform spectrum of propyne-d3 (CD3CCH) at room temperature has been recorded in the region of the ν7 band (950–1200 cm−1) at an apodized resolution of 0.004 cm−1. About 2400 lines consisting of a total of 25 sub-bands ranging from KΔK = −13 to 12 have been assigned in the ν7 band of CD3CCH. In the fitting analysis, the ν4 = 1 state to which transitions have not been identified in the experimental spectrum included as a “shadow” state. The data have been analyzed taking into account of the strong x-y Coriolis interaction of the ν7 = 1 state with the ν4 = 1 state. l-type interactions between the ±l components of the ν7 = 1 state, and a weak k-type doubling interaction between ν7 = 1 and ν4 = 1 states have been included in the analysis. The vibration-rotation transitions for K ≥ 8 show fairly large amount of deviation and most likely interacted by other nearby states. The transitions upto K = 7 and Jmax = 61 could be fitted with a standard deviation of 0.0007 cm−1.

Accurate Frequency Determination of Vibration-Rotation and Rotational Transitions of SiH.

The fundamental 28SiH+ ion has been characterized in a collaborative work, utilizing a hollow-cathode-discharge laser-spectrometer and a cryogenic ion trap spectrometer. Twenty-three vibration-rotation transitions around 4.75 μm have been detected with high accuracy. This has facilitated the first direct measurement of the pure rotational transition J = 1 ← 0 at 453056.3632(4) MHz in the trap spectrometer. The measured and accurately predicted transitions enable the search for this ion in space with IR and sub-mm telescopes.

ExoMol line lists XXIV: a new hot line list for silicon monohydride, SiH

SiH has long been observed in the spectrum of our Sun and other cool stars. Computed line lists for the main isotopologues of silicon monohydride, $^{28}$SiH, $^{29}$SiH, $^{30}$SiH and $^{28}$SiD are presented. These line lists consider rotation-vibration transitions within the ground $X$ $^{2}\Pi$ electronic state as well as transitions to the low-lying $A$ $^{2}\Delta$ and $a$ $^{4}\Sigma^-$ states. Ab initio potential energy (PECs) and dipole moment curves (DMCs) along with spin-orbit and electronic-angular-momentum couplings between them are calculated using the MRCI level of theory with the MOLPRO package. The PEC for the ground X $^2\Pi$ state is refined to available experimental data with a typical accuracy of around 0.01 cm$^{-1}$ or better. The $^{28}$SiH line list includes 11,785 rovibronic states and 1,724,841 transitions with associated Einstein-A coefficients for angular momentum $J$ up to $82.5$ and covering wavenumbers up to 31340 cm$^{-1}$ ($\lambda$ $<$ 0.319 $\mu$m). Spectra are simulated using the new line list and comparisons made with various experimental spectra. These line lists are applicable up to temperatures of ~5000 K, making them relevant to astrophysical objects such as exoplanetary atmospheres and cool stars and opening up the possibility of detection in the interstellar medium. These line lists are available at the ExoMol www.exomol.com and CDS database websites.

Spectral characteristics of multi-line Q-switched CO laser radiation frequency converted in ZnGeP2

Lasing on different spectral lines belonging to a giant pulse of multi-line Q-switched CO laser was experimentally studied. The Q-switched CO laser emitted a giant microsecond pulse that consisted of about one hundred subpulses corresponding to different rotational–vibrational transitions. Amplitude, time delay and duration were measured for such a laser subpulse, and processes affecting formation of the CO laser giant pulse spectrum were analyzed. These data were taken into account to correctly estimate peak power and the number of spectral lines of radiation formed under sum frequency conversion of the CO laser radiation in nonlinear ZnGeP2 crystal.

Quantum optimal control of the isotope-selective rovibrational excitation of diatomic molecules

We carry out optimal control theory calculations for isotope-selective pure rotational and vibrational-rotational excitations of diatomic molecules. The fifty-fifty mixture of diatomic isotopologues, 7Li37Cl and 7Li35Cl, is considered and the molecules are irradiated with a control pulse. In the wave packet propagation we employ the method quantum mechanically rigorous for the two-dimensional system including both the radial and angular motions. We investigate quantum controls of the isotope-selective pure rotational excitation for two total times 1280000 and 2560000a.u. (31.0 and 61.9ps) and the vibrational-rotational excitation for three total times, 640000, 1280000, and 2560000a.u. (15.5, 31.0, and 61.9ps) The initial state is set to the situation that both the isotopologues are in the ground vibrational and rotational levels, v=0 and J = 0. The target state for pure rotational excitation is set to 7Li37Cl (v=0, J = 1) and 7Li35Cl (v=0, J = 0); that for vibrational-rotational excitation is set to 7Li37Cl (v=1, J = 1) and 7Li35Cl (v=0, J = 0). The obtained final yields are quite high and those for the longest total time are calculated to be nearly 1.0. When total time is 1280000a.u., the final yields for the pure rotational excitation are slightly smaller than those for the vibrational-rotational excitation. This is because the isotope shift (difference in transition energy between the two isotopologues) for the pure rotational transition between low-lying levels is much smaller than that for the vibrational-rotational transition. We thus theoretically succeed in controlling the isotope-selective excitations of diatomic molecules using the method including both radial and angular motions quantum mechanically.

Direct-comb molecular spectroscopy by heterodyne detection with continuous-wave laser for high sensitivity.

We have demonstrated direct-comb molecular spectroscopy in which an individual-comb mode is resolved by heterodyne detection with a continuous-wave (cw) laser. This simple, fast, and sensitive technique was demonstrated for atomic spectroscopy in [ Appl. Phys. Lett.101, 051105 ( 2012)], but is more suitable for molecular spectroscopy. Four rotation-vibration transitions of methane have simultaneously been recorded in a Doppler-limited resolution using a spectrally broadened comb based on an Er-doped fiber laser and a cw 1651-nm distributed-feedback laser diode. Even though the power level of the comb modes and the sample absorption are weaker than those of the previous studies, in this work the cw laser frequency is stabilized to one of the comb modes, and the data are thereby averaged for extended periods of time, resulting an improvement in sensitivity.

Calculation of the vibration–rotational transition intensities of water molecules trapped in an argon matrix: stretching O–H vibrations spectral region

ABSTRACTThe frequencies and intensities of vibration–rotational transitions of water molecules in an argon matrix were calculated for temperatures of 6 and 30 K. The rigid asymmetric top approximation was used with available literature values of the effective rotational constants in the ground and excited vibrational states. The calculations were carried out by taking into account the existence of a non-equilibrium population distribution between the rotational levels of ortho- and para-water isomers. It was assumed that the temperature relaxation of the population of rotational levels is independent of the ortho- and para-isomers. Comparison of the results of the theoretical calculations with experimental literature data shows good agreement for the majority of the rotational structure lines for symmetric and antisymmetric stretching vibrations both in the frequency values and in the values of the relative intensities.

Comment on the paper “NDSD-1000: High-resolution, high-temperature nitrogen dioxide spectroscopic Databank” by A.A. Lukashevskaya, N.N. Lavrentieva, A.C. Dudaryonok, V.I. Perevalov, J Quant Spectrosc Radiat Transfer 2016;184:205–17

A recent paper [1] presents a high-resolution, high-temperature version of the Nitrogen Dioxide Spectroscopic Databank called NDSD-1000. The NDSD-1000 database contains line parameters (positions, intensities, self- and air-broadening coefficients, exponents of the temperature dependence of self- and air-broadening coefficients) for numerous cold and hot bands of the 14N16O2 isotopomer of nitrogen dioxide. The parameters used for the line positions and intensities calculation were generated through a global modeling of experimental data collected in the literature within the framework of the method of effective operators. However, the form of the effective dipole moment operator used to compute the NO2 line intensities in the NDSD-1000 database differs from the classical one used for line intensities calculation in the NO2 infrared literature [12]. Using Fourier transform spectra recorded at high resolution in the 6.3µm region, it is shown here, that the NDSD-1000 formulation is incorrect since the computed intensities do not account properly for the (Int(+)/Int(−)) intensity ratio between the (+) (J=N+ 1/2) and (−) (J=N−1/2) electron – spin rotation subcomponents of the computed vibration rotation transitions. On the other hand, in the HITRAN or GEISA spectroscopic databases, the NO2 line intensities were computed using the classical theoretical approach, and it is shown here that these data lead to a significant better agreement between the observed and calculated spectra.

High sensitivity Cavity Ring Down Spectroscopy of the 2ν1 + 3ν2 + ν3 band of NO2 near 1.57 µm

The weak 2ν1+3ν2+ν3absorption band of the nitrogen dioxide main isotopologue (14N16O2) is investigated near 6350cm−1. The absorption spectrum was recorded by high sensitivity Cavity Ring Down Spectroscopy with a noise equivalent absorption of αmin ≈ 1 × 10−10cm−1. In total, 1069 lines of the 2ν1 +3ν2 +ν3 band were assigned with rotational quantum numbers N and Ka up to 48 and 8, respectively, that corresponds to 1276 vibration-rotation transitions. The derived set of line positions is reproduced with an effective Hamiltonian with an rms of 2.35 × 10−3cm−1 for the (obs.-calc.) deviations. The effective Hamiltonian takes explicitly into account the Coriolis interactions between the spin rotational levels of the (2,3,1) upper vibrational state and those of two nearby dark states - (2,5,0) and (2,1,2) - together with the electron spin-rotation interactions. Using the corresponding eigenfunctions the principal effective dipole moment parameter responsible for the line intensities of the 2ν1 +3ν2 +ν3 band is fitted to selected measured line intensities which are reproduced with an rms deviation of 6.2%.

Information system for molecular spectroscopy: 6—systematization of spectral data on deutero-substituted isotopologues of the hydrogen sulfide molecule

Properties of data published on the spectral line parameters for deutero-substituted isotopologues of the hydrogen sulfide molecule (HDS, HD34S, D2S, and D2 34S) are described. Most properties follow from the results of vacuum wavenumber quality analysis. Two applications used for the data quality analysis in W@DIS information system are described. The results of computer-based data quality analysis of vacuum wavenumbers are completed by the expert evaluation of the quality of the same data set. The rotation-vibrational transitions and energy levels of deutero-substituted isotopologues of the hydrogen sulfide molecule are imported into the database; their properties are collected in the knowledge base and available in the W@DIS information system (http://wadis.saga.iao.ru/).

Theoretical and experimental analyses of the TEA CO2 lasers dynamics by six temperature vibrational-rotational model

A six-temperature dynamic model, modified in terms of vibrational-rotational transitions, has been used to describe the dynamic processes in TEA CO2 lasers. Significant improvement in the predicted laser characteristics was obtained, taking into account the CO2 molecules vibrational-rotational transitions. The coupled differential equations were numerically solved by the fourth order Runge–Kutta method. The simulated output characteristics of the laser have been compared with simple vibrational dynamics model and experimental data due to a homemade TEA CO2 laser. It has been found that the best agreement with experimental results regards to the vibrational-rotational dynamic model.

Laser-induced optical breakdown spectroscopy of polymer materials based on evaluation of molecular emission bands

Laser-induced breakdown spectroscopy (LIBS) for composition analysis of polymer materials results in optical spectra containing atomic and ionic emission lines as well as molecular emission bands. In the present work, the molecular bands are analyzed to obtain spectroscopic information about the plasma state in an effort to quantify the content of different elements in the polymers. Polyethylene (PE) and a rubber material from tire production are investigated employing 157nmF2 laser and 532nm Nd:YAG laser ablation in nitrogen and argon gas background or in air. The optical detection reaches from ultraviolet (UV) over the visible (VIS) to the near infrared (NIR) spectral range. In the UV/VIS range, intense molecular emissions, C2 Swan and CN violet bands, are measured with an Echelle spectrometer equipped with an intensified CCD camera. The measured molecular emission spectra can be fitted by vibrational-rotational transitions by open access programs and data sets with good agreement between measured and fitted spectra. The fits allow determining vibrational-rotational temperatures. A comparison to electronic temperatures Te derived earlier from atomic carbon vacuum-UV (VUV) emission lines show differences, which can be related to different locations of the atomic and molecular species in the expanding plasma plume. In the NIR spectral region, we also observe the CN red bands with a conventional CDD Czerny Turner spectrometer. The emission of the three strong atomic sulfur lines between 920 and 925nm is overlapped by these bands. Fitting of the CN red bands allows a separation of both spectral contributions. This makes a quantitative evaluation of sulfur contents in the start material in the order of 1wt% feasible.