Overtone Spectra Research Articles

Photonic Monitoring of Atmospheric and Aquatic Fauna

AbstractFlying insects are of utmost importance in ecology and for human living conditions. Certain species serve as indispensable pollinators to ensure the availability of food stuffs, while others are dangerous vectors for spreading deadly diseases, such as malaria. Agricultural pests reduce the yield of crops, and their abatement through pesticides cause many additional problems. Birds and bats are frequently carriers of diseases, which, especially for long‐distance migrants, cause serious consequences. Clearly, there is high motivation to be able to effectively identify and quantify flying fauna. Here, the emerging field of optics and laser‐based monitoring of flying fauna is reviewed with an emphasis on remote sensing based on pulsed and contineous wave (CW) lidar systems, and how they complement existing radar techniques. Furthermore, ground‐truth laboratory studies are covered. Wing‐beat and overtone spectra as well as reflectance, depolarization and fluorescence properties are studied. The aquatic environment is for many reasons less accessible for optical studies, but is clearly also of great importance. Phytoplankton constitute the start of the aquatic food chain, followed by zooplankton and a long chain of higher animals, including fish, an important part of the human food supply. Finally, how optical monitoring can complement sonar and sampling techniques is discussed.

The specificity of interpreting the image of Vassili from the opera “Siberia” by Umberto Giordano

The specificity of interpreting the image of Vassili from the opera “Siberia” by Umberto Giordano

A tunable time-resolved spontaneous Raman spectroscopy setup for probing ultrafast collective excitation and quasiparticle dynamics in quantum materials.

We present a flexible and efficient ultrafast time-resolved spontaneous Raman spectroscopy setup to study collective excitation and quasi-particle dynamics in quantum materials. The setup has a broad energy tuning range extending from the visible to near infrared spectral regions for both the pump excitation and Raman probe pulses. Additionally, the balance between energy and time-resolution can be controlled. A high light collecting efficiency is realized by high numerical aperture collection optics and a high-throughput flexible spectrometer. We demonstrate the functionality of the setup with a study of the zone-center longitudinal optical phonon and hole continuum dynamics in silicon and discuss the role of the Raman tensor in time-resolved Raman scattering. In addition, we show an evidence for unequal phonon softening rates at different high symmetry points in the Brillouin zone of silicon by means of detecting pump-induced changes in the two-phonon overtone spectrum. Demagnetization dynamics in the helimagnet Cu2OSeO3 is studied by observing softening and broadening of a magnon after photo-excitation, underlining the unique power of measuring transient dynamics in the frequency domain, and the feasibility to study phase transitions in quantum materials.

Correction to "Role of Torsion-Vibration Coupling in the Overtone Spectrum and Vibrationally Mediated Photochemistry of CH3OOH and HOOH".

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “Role of Torsion-Vibration Coupling in the Overtone Spectrum and Vibrationally Mediated Photochemistry of CH3OOH and HOOH”Laura C. DzuganLaura C. DzuganMore by Laura C. Dzugan, Jamie MatthewsJamie MatthewsMore by Jamie Matthews, Amitabha Sinha*Amitabha SinhaMore by Amitabha Sinhahttp://orcid.org/0000-0002-2179-209X, and Anne B. McCoy*Anne B. McCoyMore by Anne B. McCoyhttp://orcid.org/0000-0001-6851-6634Cite this: J. Phys. Chem. A 2018, 122, 21, 4909Publication Date (Web):May 17, 2018Publication History Published online17 May 2018Published inissue 31 May 2018https://doi.org/10.1021/acs.jpca.8b04048Copyright © 2018 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views463Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (227 KB) Get e-Alerts Get e-Alerts

Linear and Nonlinear Thermal Lens Signal of the (Δν = 6) C-H Vibrational Overtone of Naphthalene in Liquid Solutions of n-Hexane.

The thermal lens technique is applied to vibrational overtone spectroscopy of solutions of naphthalene (C10H8) in liquid hexane. The C-H fifth vibrational (Δν = 6) overtone spectrum of C10H8 is detected at room temperature for mole fractions from 0.08 to 19 × 10-6 using n-C6H14 as solvent. By detecting the absorption band in a 19 ppm (parts per million) solution, the peak absorption of the signal is approximately (2.2 ± 0.3) × 10-7 cm-1. A plot of normalized integrated intensity as a function of the mole fraction of naphthalene in solution reveals a dependence of the magnitude of the signal with the probe laser wavelength. If the wavelength of the probe laser is 568 nm, the thermal lens signal (TLS) is linear as a function of the mole fraction of the solution. When the wavelength of the probe laser is 488 nm, the TLS is nonlinear as a function of the concentration. Three different models of nonlinear absorption are discussed. A two-color absorption model that includes the simultaneous absorption of the pump and probe lasers could explain the enhanced magnitude and the nonlinear behavior of the TLS for solutions of mole fraction < 0.1%.

Dynamics of the OH stretching mode in crystalline Ba(ClO4)2·3H2O.

The vibrational dynamics of the OH stretching mode in Ba(ClO4)2 trihydrate are investigated by means of femtosecond infrared spectroscopy. The sample offers plane cyclic water trimers in the solid phase that feature virtually no hydrogen bond interaction between the water molecules. Selective excitation of the symmetric and asymmetric stretching leads to fast population redistribution, while simultaneous excitation yields quantum beats, which are monitored via a combination tone that dominates the overtone spectrum. The combination of steady-state and time-resolved spectroscopy with quantum chemical simulations and general theoretical considerations gives indication of various aspects of symmetry breakage. The system shows a joint population lifetime of 8 ps and a long-lived coherence between symmetric and asymmetric stretching, which decays with a time constant of 0.6 ps.

Role of Torsion-Vibration Coupling in the Overtone Spectrum and Vibrationally Mediated Photochemistry of CH3OOH and HOOH

The yield of vibrationally excited OH fragments resulting from the vibrationally mediated photodissociation of methyl hydroperoxide (CH3OOH) excited in the vicinity of its 2νOH and 3νOH stretching overtones is compared with that resulting from excitation of the molecule to states with three quanta in the CH stretches and to the state with two quanta in the OH stretch and one in the OOH bend (2νOH + νOOH). We find that the OH fragment vibrational state distribution depends strongly on the vibrational state of CH3OOH prior to photodissociation. Specifically, dissociation from the CH stretch overtones and the stretch/bend combination band involving the OH stretch and OOH bend produced significantly less vibrationally excited OH fragments compared to that produced following excitation of CH3OOH to an overtone in the OH stretch. While the absence of vibrationally excited OH photoproducts following excitation of the CH overtone is not surprising, the lack of vibrationally excited OH following excitation to the 2νOH+νOOH combination band is unexpected given that photodissociation following excitation to the lower-energy 2νOH state produces OH products in v = 1 as well as in its ground state. This trend persists even when the electronic photodissociation wavelength is changed from 532 to 355 nm and thus suggests that the observed disparity arises from differences in the nature of the initially populated vibrational states. This lack of vibrationally excited OH products likely reflects the enhanced intramolecular vibrational energy redistribution associated with the stretch/bend combination level compared to the pure OH stretch overtone. Consistent with this hypothesis, photodissociation from the stretch/bend combination level of the smaller HOOH molecule produces more vibrationally excited OH fragments compared to that resulting from the corresponding state of CH3OOH. These results are investigated using second-order vibrational perturbation theory based on an internal coordinate representation of the normal modes. Consistent with the observations, the first-order correction to the wave function shows stronger coupling of the 2νOH+νOOH state to states with torsion excitation compared to the other bands considered in this study.

A model for the observed decorrelation of partials in the overtone spectra of bowed stringed instruments

It has been shown that the overtone frequencies in the spectra of bowed stringed instruments played with vibrato exhibit less than perfect pairwise correlations. However, these results are inconsistent with the mechanism of performing vibrato by changing the length of the string. Since modulating the string length affects the frequencies of all string modes proportionately, it is curious that the overtones exhibit less than perfect correlations. The observed decorrelations, therefore, may be attributed to the filtering of the string’s vibrations by the mechanical-acoustic resonant modes of the instrument body. The exact frequency deviations depend upon the frequencies of instrument’s resonant modes in relation to the string’s overtone frequencies and the width and rate of the vibrato. By modelling the instrument body as a sum of resonant modes driven by a frequency modulated saw tooth wave, we develop an analytical model relating the observed frequency deviations to the modal properties of the instrument....

Intramolecular hydrogen-bonding effects on O[sbnd]H stretch overtone excitation for fluorinated hydroperoxides

Applying computational methods for predicting gas-phase OH stretch overtone spectra to the series of fluorinated hydroperoxides CF3OOH, CHF2OOH, and CH2FOOH reveals how intramolecular hydrogen bonding changes their overtone photochemistry, relative to their un-fluorinated analog CH3OOH. Intramolecular hydrogen bonding between fluorine and the hydroxyl hydrogen atom decreases OH stretch frequencies and raises the barrier for torsion about the OO bond. Whereas OO torsion accompanies OH stretch overtone excitation for CH3OOH, this is not the case for the fluorinated analogs that have intramolecular hydrogen bonding. The comparison highlights the molecular features that contribute to the feasibility of atmospheric overtone-induced OO bond dissociation for CH3OOH, but not for its fluorinated analogs.

Near infrared overtone (vOH = 2 ← 0) spectroscopy of Ne-H2O clusters.

Vibrationally state selective overtone spectroscopy and dynamics of weakly bound Ne-H2O complexes (D0(para) = 31.67 cm-1, D0(ortho) = 34.66 cm-1) are reported for the first time, based on near infrared excitation of van der Waals cluster bands correlating with vOH = 2 ← 0 overtone transitions (|02-⟩←|00+⟩ and |02+⟩←|00+⟩) out of the ortho (101) and para (000) internal rotor states of the H2O moiety. Quantum theoretical calculations for nuclear motion on a high level ab initio potential energy surface (CCSD(T)/VnZ-f12 (n = 3,4), corrected for basis set superposition error and extrapolated to the complete basis set limit) are employed for assignment of Σ←Σ,Π←Σ, and Σ←Π infrared bands in the overtone spectra, where Σ(K = 0) and Π (K = 1) represent approximate projections (K) of the body angular momentum along the Ne-H2O internuclear axis. End-over-end tumbling of the ortho Ne-H2O cluster is evident via rotational band contours observed, with band origins and rotational progressions in excellent agreement with ab initio frequency and intensity predictions. A clear Q branch in the corresponding |02+⟩fΠ(111)←eΣ(000) para Ne-H2O spectrum provides evidence for a novel e/f parity-dependent metastability in these weakly bound clusters, in agreement with ab initio bound state calculations and attributable to the symmetry blocking of an energetically allowed channel for internal rotor predissociation. Finally, Boltzmann analysis of the rotational spectra reveals anomalously low jet temperatures (Trot ≈ 4(1) K), which are attributed to "evaporative cooling" of weakly bound Ne-H2O clusters and provide support for similar cooling dynamics in rare gas-tagging studies.

Ab Initio Vibrational Spectroscopy of cis- and trans-Formic Acid from a Global Potential Energy Surface.

A global analytic potential energy surface for the ro-vibrational dynamics of cis- and trans-formic acid is presented, constructed using LASSO-based regression to reproduce CCSD(T)(F12*)/cc-pVTZ-F12 energies. The fit is accurate to 0.25% has an RMS deviation from the ab initio data of 9 cm-1 for the energy range 0-15000 cm-1. Converged J = 0 vibrational eigenstates are reported, computed using vibrational configuration interaction with an internal coordinate path Hamiltonian for the torsional motion connecting the cis and trans rotamers. Methodological choices concerning the appropriate definitions of the curvilinear and diabatic bath coordinates are discussed. The zero point of the cis rotamer is 1412 cm-1 above that of the trans, which lies at 7354 cm-1. The computed fundamentals match the bands recorded from gas-phase IR spectroscopy with an RMSD of only 3 cm-1. A fresh assignment of the overtone spectra of both the cis and trans rotamers is presented for the energy range 0-4720 cm-1, where 14 out of the 51 bands are reassigned on the basis of the VCI calculations.

An application of multiple-stage non-negative matrix factorization to music analysis

Non-negative matrix factorization (NMF) is an analysis technique for matrix with non-negative elements. NMF decomposes a sound spectrogram X obtained by a short-time Fourier transform into the product of two non-negative matrices H and U. The matrix H represents the bases of X and the matrix U represents the activation gains of H. As an extension of NMF, multiple-stage NMF has been proposed in order to represent the hierarchy of data. This research focuses on the hierarchy of music data, and attempts to apply multiple-stage NMF to music analysis. For simplicity, sounds treated in this research are assumed as follows: single tone consists of fundamental tone and harmonic overtones and a chord consists of some single tones. According to this assumption, observed sound spectrogram can be decomposed into three stages. In the first stage, the basis matrix is approximated by a Gaussian distribution in order to represent a spectrum of fundamental tone and harmonic overtones. In the second stage, the basis matrix consists of the set of single tone with fundamental tone and harmonic overtones. And in the third stage, the basis matrix consists of the set of chord with some single tones. Evaluation was carried out by MIDI data.

Observer-based feedback linearisation of nonlinear ultrasonic systems

At high vibration amplitudes, piezoelectric transducers exhibit nonlinear characteristics (Blackburn and Cain, J Appl Phys 100:114101, 2006; Aurelle et al., Ultrasonics 34:187–191, 1996; Hall, J Mater Sci 36:4575–4601, 2001) due to its material properties. The result is a resonance frequency shift and the occurrence of the jump phenomenon. The jump phenomenon may cause a collapse of the vibration amplitude in forced excitation systems. This nonlinear behaviour is often associated with a discrete spectrum of overtones. In order to linearise the nonlinear system a control circuit was implemented with the aim to eliminate the overtones in the response of the nonlinear system. This paper gives a theoretical and experimental study of damping higher harmonics using a discrete Luenberger observer implemented in a feedback linearisation loop. The Luenberger observer monitors the electrical charge which is proportional to the displacement and uses this information to generate a feedback voltage in order to achieve linear behaviour. Thus, the observer’s output is used to create a linearisation term added to the excitation voltage to eliminate the nonlinearity. In relation to the linearised system, there is no occurence of the jump phenomenon and the phase is linear within the operation band. This simplifies the implementation of a resonance control system.

Nonlinear thermal lens signal of the (Δυ = 6) C–H vibrational overtone of C6H6 in liquid solutions of n-C6H14 and CCl4

The thermal lens technique is applied to vibrational overtone spectroscopy of solutions of benzene. The pump and probe thermal lens technique has been found to be very sensitive for detecting samples of low concentration in transparent solvents. The C–H fifth vibrational (Δυ = 6) overtone spectrum of benzene is detected at room temperature for compositions per volume in the range (1 to 1 × 10−4) using CCl4 and n-C6H14 as solvents. By detecting the absorption band in a 100-ppm solution, the peak absorption of the signal is approximately (2.2 ± 0.3) × 10−7 cm−1. The parameters that determine the magnitude of the thermal lens signal such as the pump laser power and the thermodynamic properties of the solvent and solute are discussed. A plot of normalized integrated intensity as a function of composition of benzene in solution reveals a nonlinear behavior. The nonlinearity cannot be explained assuming solvent enhancement at low concentrations. A two-color absorption model that includes the simultaneous absorption of the pump and probe lasers explains the enhanced magnitude and the nonlinear behavior of the thermal lens signal for solutions of composition below 0.01.

Realistic Instrumentation Platform for Active and Passive Optical Remote Sensing.

We describe the development of a novel versatile optical platform for active and passive remote sensing of environmental parameters. Applications include assessment of vegetation status and water quality. The system is also adapted for ecological studies, such as identification of flying insects including agricultural pests. The system is based on two mid-size amateur astronomy telescopes, continuous-wave diode lasers at different wavelengths ranging from violet to the near infrared, and detector facilities including quadrant photodiodes, two-dimensional and line scan charge-coupled device cameras, and a compact digital spectrometer. Application examples include remote Ramanlaser-induced fluorescence monitoring of water quality at 120 m distance, and insect identification at kilometer ranges using the recorded wing beat frequency and its spectrum of overtones. Because of the low cost this developmental platform is very suitable for advanced research projects in developing countries and has, in fact, been multiplied during hands-on workshops and is now being used by a number of groups at African universities.

Peculiarities of high-overtone transition probabilities in carbon monoxide revealed by high-precision calculation.

In the recent work devoted to the calculation of the rovibrational line list of the CO molecule [G. Li et al., Astrophys. J., Suppl. Ser. 216, 15 (2015)], rigorous validation of the calculated parameters including intensities was carried out. In particular, the Normal Intensity Distribution Law (NIDL) [E. S. Medvedev, J. Chem. Phys. 137, 174307 (2012)] was employed for the validation purposes, and it was found that, in the original CO line list calculated for large changes of the vibrational quantum number up to Δn = 41, intensities with Δn > 11 were unphysical. Therefore, very high overtone transitions were removed from the published list in Li et al. Here, we show how this type of validation is carried out and prove that the quadruple precision is indispensably required to predict the reliable intensities using the conventional 32-bit computers. Based on these calculations, the NIDL is shown to hold up for the 0 → n transitions till the dissociation limit around n = 83, covering 45 orders of magnitude in the intensity. The low-intensity 0 → n transition predicted in the work of Medvedev [Determination of a new molecular constant for diatomic systems. Normal intensity distribution law for overtone spectra of diatomic and polyatomic molecules and anomalies in overtone absorption spectra of diatomic molecules, Institute of Chemical Physics, Russian Academy of Sciences, Chernogolovka, 1984] at n = 5 is confirmed, and two additional "abnormal" intensities are found at n = 14 and 23. Criteria for the appearance of such "anomalies" are formulated. The results could be useful to revise the high-overtone molecular transition probabilities provided in spectroscopic databases.

Thermochemistry of HO2 + HO2 → H2O4: Does HO2 Dimerization Affect Laboratory Studies?

Self-reaction is an important sink for the hydroperoxy radical (HO2) in the atmosphere. It has been suggested (Denis, P. A.; Ornellas, F. R. J. Phys. Chem. A, 2009, 113 (2), 499-506) that the minor product hydrogen tetroxide (HO4H) may act as a reservoir of HO2. Here, we compute the thermochemistry of HO2 self-reactions to determine if either HO4H or the cyclic hydrogen-bound dimer (HO2)2 can act as reservoirs. We computed electronic energies using coupled-cluster calculations in the complete basis set limit, CCSD(T)/CBS[45]//CCSD(T)/cc-pVTZ. Our model chemistry includes corrections for vibrational anharmonicity in the zero-point energy and vibrational partition functions, core-valence correlation, scalar relativistic effects, diagonal Born-Oppenheimer, spin-orbit splitting, and higher-order corrections. We compute the Gibbs energy of dimerization to be (-20.1 ± 1.6) kJ/mol at 298.15 K (2σ uncertainty), and (-32.3 ± 1.5) kJ/mol at 220 K. For atmospherically relevant [HO2] = 10(8) molecules per cm(3), our thermochemistry indicates that dimerization will be negligible, and thus H2O4 species are atmospherically unimportant. Under conditions used in laboratory experiments ([HO2] > 10(12) molecules per cm(3), 220 K), H2O4 formation may be significant. We compute two absorption spectra that could be used for laboratory detection of HO4H: the OH stretch overtone (near-IR) and electronic (UV) spectra.

(14)N overtone transition in double rotation solid-state NMR.

Solid-state NMR transitions involving outer energy levels of the spin-1 (14)N nucleus are immune, to first order in perturbation theory, to the broadening caused by the nuclear quadrupole interaction. The corresponding overtone spectra, when acquired in conjunction with magic-angle sample spinning, result in lines, which are just a few kHz wide, permitting the direct detection of nitrogen compounds without the need for labeling. Despite the success of this technique, "overtone" resonances are still broadened due to indirect, second order effects arising from the large quadrupolar interaction. Here we demonstrate that another order of magnitude in spectral resolution may be gained by using double rotation. This brings the width of the (14)N solid-state NMR lines much closer to the region commonly associated with high-resolution solid-state NMR spectroscopy of (15)N and demonstrates the improvements in resolution that may be possible through the development of pulsed methodologies to suppress these second order effects.

OH-stretch overtone of methanol: empirical assignment using a two temperature technique in a supersonic jet.

This paper describes a novel approach for empirical lower state assignments in complex high resolution ro-vibrational overtone spectra of molecules with low rotational constants and complex intramolecular dynamics. Methanol, CH3OH, was chosen as a representative of such molecules - it is an asymmetric top with two non-hydrogen nuclei and hindered internal rotation leading to dense and disordered rotational structure of vibrational overtone bands. We report the first rotationally resolved methanol spectra of the OH-stretch overtone 2ν1 band using sub-Doppler diode laser spectroscopy in a supersonic jet, and describe how the combination of two temperature analysis (TTA) and analysis by ground state combination differences (GSCDs) is used to reliably identify spectral lines that originate from lowest rotational states. In the first step of the analysis, the TTA was utilized to obtain a set of possible rotational assignments for each spectral line using the line intensity variation between two different temperatures in the supersonic jet (13, and 56 K respectively). Thereafter, the GSCDs were used to confirm specific lower state assignment for those spectral lines that have been identified to have low rotational ground states by the TTA. We show that the TTA pre-selection leads to fast and reliable confirmation by GSCDs and avoids false assignments due to accidental GSCD matches. The procedure yields an important subset of reliably assigned spectral lines in the complex ro-vibrational structure that provides a convenient starting point for subsequent application of traditional spectral analysis techniques.

Infrared overtone spectroscopy of adsorbed hydrogen in MOF-5

Overtone spectroscopy is used to observe the rovibrational spectra of the hydrogen isotopologues H2, HD, and D2 adsorbed in the metal–organic framework known as MOF-5. It is shown that the overtone spectrum facilitates the identification of hydrogen modes which are obscured in the fundamental region by the presence of MOF-5 features. Further, the overtone spectrum of H2 at the primary adsorption site is greatly enhanced relative to other sites, and thus ambiguities about feature assignment can be avoided. The frequency (wavenumber) of the overtone modes are in good agreement with a Buckingham perturbative model while the relative intensity of the Q2(0) pure vibrational mode is found to be anomalously large, most likely arising through mode coupling to the MOF-5 framework.