IR Emission Spectra Research Articles

Anharmonicity and deuteration in the IR absorption and emission spectrum of phenylacetylene

Anharmonic cascade emission simulations, herein evinced by full reproduction and deep insights into recent emission spectroscopy experiments of phenylacetylene, are integral to the future successful analysis of JWST observational spectra. Experimental infrared absorption experiments conducted in this study reveal a complex spectrum dominated by quantum effects that are uncovered by anharmonic computational analysis. From this work, it becomes clear that phenylacetylene exhibits strong resonance coupling between fundamental and two-quanta combination modes as well as giving indication for coupling with higher-order, three-quanta combination bands. This study benchmarks the development of advanced computational methods that will be extended to larger systems of astronomical relevance and those including isotopic substitution and side group functionalization with groups such as acetylene. The astrophysical implications of these results, including the potential for detection of acetylenic C–H stretches in space, are discussed in the vein of the impact polycyclic aromatic hydrocarbons have on astronomical infrared emission bands.

Assessment of a physics-based retrieval of exoplanet atmospheric temperatures from infrared emission spectra

Abstract Atmospheric temperatures are to be estimated from thermal emission spectra of Earth-like exoplanets orbiting M-stars as observed by current and future planned missions. To this end, a line-by-line radiative transfer code is used to generate synthetic thermal infrared (TIR) observations. The range of ‘observed’ intensities provides a rough hint of the atmospheric temperature range without any a priori knowledge. The equivalent brightness temperature (related to intensities by Planck’s function) at certain wavenumbers can be used to estimate the atmospheric temperature at corresponding altitudes. To exploit the full information provided by the measurement we generalize Chahine’s original approach and infer atmospheric temperatures from all spectral data using the wavenumber-to-altitude mapping defined by the weighting functions. Chahine relaxation allows an iterative refinement of this ‘first guess’. Analysis of the $4.3\rm \, \mu m$ and $15\rm \, \mu m$ carbon dioxide TIR bands enables an estimate of atmospheric temperatures for rocky exoplanets even for low signal to noise ratios of 10 and medium resolution. Inference of Trappist-1e temperatures is, however, more challenging especially for CO2 dominated atmospheres: the ‘standard’ $4.3\rm \, \mu m$ and $15\rm \, \mu m$ regions are optically thick and an extension of the spectral range towards atmospheric window regions is important. If atmospheric composition (essentially CO2 concentration) is known temperatures can be estimated remarkably well, quality measures such as the residual norm provide hints on incorrect abundances. In conclusion, temperature in the mid atmosphere of Earth-like planets orbiting cooler stars can be quickly estimated from thermal IR emission spectra with moderate resolution.

Infrared Spectra of Small Radicals for Exoplanetary Spectroscopy: OH, NH, CN and CH: The State of Current Knowledge.

In this study, we present a current state-of-the-art review of middle-to-near IR emission spectra of four simple astrophysically relevant molecular radicals-OH, NH, CN and CH. The spectra of these radicals were measured by means of time-resolved Fourier transform infrared spectroscopy in the 700-7500 cm-1 spectral range and with 0.07-0.02 cm-1 spectral resolution. The radicals were generated in a glow discharge of gaseous mixtures in a specially designed discharge cell. The spectra of short-lived radicals published here are of great importance, especially for the detailed knowledge and study of the composition of exoplanetary atmospheres in selected new planets. Today, with the help of the James Webb telescope and upcoming studies with the help of Plato and Ariel satellites, when the investigated spectral area is extended into the infrared spectral range, it means that detailed knowledge of the infrared spectra of not only stable molecules but also the spectra of short-lived radicals or ions, is indispensable. This paper follows a simple structure. Each radical is described in a separate chapter, starting with historical and actual theoretical background, continued by our experimental results and concluded by spectral line lists with assigned notation.

Near-Infrared Transitions from the Singlet Excited States to the Ground Triplet State of the S2 Molecule

Intensity of transitions from the b1∑g+ and a1Δg states to the ground state X3∑g− in the near IR emission spectrum of the S2 molecule has been calculated by the multireference configuration interaction method taking into account spin-orbit coupling (SOC). The intensity of the b1∑g+ − X3∑g,Ms=±1− transition is largely determined by the spin interaction with the electromagnetic wave, which comes from the zero-field splitting of the ground X multiplet and the SOC-induced mixing between b and X3∑g,0− states. The Einstein coefficients for the experimentally detected 0−0, 0−1, 1−1 bands of the b1∑g+−X3∑g,Ms=±1− emission system are calculated in good agreement with observations. The Einstein coefficient of the a1∆g−X3∑g,Ms=±1− magnetic dipole transition is very low, being equal to 0.0014 s−1. Nonetheless, the weakest of all experimentally observed bands (the 0−0 band of the a-XMs=±1 transition) qualitatively corresponds to this calculation. Most importantly, we provide many other IR bands for magnetic dipole b1∑g+ − X3∑g,Ms=±1− and a1∆g−X3∑g,Ms=±1− transitions, which could be experimentally observable in the S2 transparency windows from a theoretical point of view. We hope that these results will contribute to the further experimental exploration of the magnetic infrared bands in the S2 dimer.

Influence of the Combined Magnetic Field and High Dilution Technology on the Intrinsic Emission of Aqueous Solutions

Liquids prepared by sequential multiple dilutions with mechanical action (highly diluted or HD solutions) are able to influence certain properties of adjacent solutions without direct contact, which is mediated by their emission in the infrared (IR) frequency range. These properties do not manifest when HD solutions are prepared in a geomagnetic field-free chamber. Here we studied the influence of a magnetic field and the intensity of mechanical treatment on the intrinsic emission of HD solutions of antibodies (Ab) to IFNγ and their effect on the adjacent water. IR-emission spectra were recorded using a Fourier-transform IR spectrometer. Magnetic field treatment reduced the intrinsic emission intensity of all HD samples; non-contact incubation with HD Ab prepared with intense (iHD Ab) shaking or gentle (gHD Ab) mixing reduced the emission intensity of HD water as well. The emission intensity of intact water was affected only by iHD Ab. Pre-treatment of HD Ab with a magnetic field did not modify their non-contact effect on intact water. We confirmed the presence of a non-contact effect and determined what factors it depends on (treatment with a magnetic field and the intensity of shaking when preparing HD solutions). The intensity of water emission both in the presence of HD Ab and in the presence of a magnetic field changes in a similar way.

Laboratory IR Spectra of the Ionic Oxidized Fullerenes C60O+ and C60OH.

We present the first experimental vibrational spectra of gaseous oxidized derivatives of C60 in protonated and radical cation forms, obtained through infrared multiple-photon dissociation spectroscopy using the FELIX free-electron laser. Neutral C60O has two nearly iso-energetic isomers: the epoxide isomer in which the O atom bridges a CC bond that connects two six-membered rings and the annulene isomer in which the O atom inserts into a CC bond connecting a five- and a six-membered ring. To determine the isomer formed for C60O+ in our experiment—a question that cannot be confidently answered on the basis of the DFT-computed stabilities alone—we compare our experimental IR spectra to vibrational spectra predicted by DFT calculations. We conclude that the annulene-like isomer is formed in our experiment. For C60OH+, a strong OH stretch vibration observed in the 3 μm range of the spectrum immediately reveals its structure as C60 with a hydroxyl group attached, which is further confirmed by the spectrum in the 400–1600 cm–1 range. We compare the experimental spectra of C60O+ and C60OH+ to the astronomical IR emission spectrum of a fullerene-rich planetary nebula and discuss their astrophysical relevance.

Radiative relaxation in isolated large carbon clusters: Vibrational emission versus recurrent fluorescence.

Recurrent fluorescence (RF) from isolated carbon clusters containing between 24 and 60 atoms is theoretically investigated as a function of internal energy, cluster size, and structural features. The vibrational relaxation kinetics and the associated IR emission spectra are determined by means of a Monte Carlo approach with vibrational density of states computed in the harmonic approximation. RF is generally found to be highly competitive with vibrational emission. The behaviors predicted for clusters of various sizes and archetypal structures indicate that the IR emission spectra are strongly influenced by RF, an energy gap law being obtained for the evolution of the RF rate constant depending on the electronic excitation state. The present results are relevant to the photophysics of the interstellar medium and could contribute to elucidating the carriers of the extended red emission bands and the continuum emission lying below the aromatic infrared bands believed to originate from mixed aromatic-aliphatic compounds.

The Infrared Spectrum of Protonated C70

Abstract With the detection of C60, C70, and in the interstellar medium, fullerenes are currently the largest molecules identified in space. The relatively high proton affinities of C60 and C70 support the hypothesis that protonated fullerenes may also be abundant in the interstellar matter. Here, we present the first experimental vibrational spectrum of C70H+, recorded in the gas phase. The attachment of a proton to C70 causes a drastic symmetry lowering, which results in a rich vibrational spectrum. As compared to C60, where all C-atoms are equivalent due to the icosahedral symmetry, C70 belongs to the D5h point group and has five nonequivalent C-atoms, which are available as protonation sites. Combined analysis of the experimental spectrum and spectra computed at the density functional theory level enables us to evaluate the protonation isomers being formed. We compare the IR spectra of C60H+ and C70H+ to IR emission spectra from planetary nebulae, which suggests that a mixture of these fullerene analogs could contribute to their IR emission.

Energy transfer along Müller cell intermediate filaments isolated from porcine retina: I. Excitons produced by ADH1A dimers upon simultaneous hydrolysis of two ATP molecules

IR exciton propagation was explored in Müller cell (MC) intermediate filaments (IFs) filling a capillary matrix. These IFs have been isolated from porcine retina using different methods, while their properties were almost identical. Therefore, IFs isolated from the whole retinas were used presently. IR excitons were generated by IR radiation at 2 μm wavelength, or by enzymatic ATP hydrolysis, with the energy transferred to IFs. Excitons produced by ATP hydrolysis required simultaneous energy contribution of two ATP molecules, indicating simultaneous hydrolysis of two ATP molecules in the naturally dimeric human alcohol dehydrogenase enzyme (ADH1A). ATP hydrolysis was thus catalyzed by ADH1A…NAD+ enzymatic complexes absorbed at the IF extremities protruding out of the capillary matrix. The IR emission spectra of excitons were dependent on the exciton generation method. We believe this resulted from the exciton energy distribution varying in function of the generation method used. The latter seems reasonable, given the very long excited-state lifetimes, implying low nonradiative relaxation rates. The energy liberated by ATP hydrolysis has been measured directly in these experiments, for the first time. The results demonstrate that contrary to the predictions of equilibrium thermodynamics, the liberated energy is independent on the ATP/ADP concentration ratio, indicating that non-equilibrium reactions take place. Time-resolved experiments with excitons produced by pulsed IR radiation evaluated characteristic exciton propagation and emission times. For the first time, biexcitonic processes were observed in biological objects, whereby simultaneous hydrolysis of two ATP molecules bound to the same dimeric ADH1A molecule generated excitons carrying twice the energy liberated by hydrolysis of a single ATP molecule. The results reported indicate that ATP-liberated energy may be transmitted along natural polypeptide nanofibers in vivo, within and between live cells. These ideas could promote new understanding of the biophysics of life.

Study of the microscopic mechanism of Ir(ppy)$_{3}$ regulating exciton splitting and luminescence process in Rubrene

To explore the microscopic mechanism of singlet exciton splitting (${\\rm~S}_{1}+{\\rm~S}_{0}\\to~{\\rm~T}_{1}+~{\\rm~T}_{1}$, STT) and luminescence in Rubrene, a phosphorescent material Ir(ppy)$_{3}$ with strong spin-orbit coupling (SOC) and green emission was selected and mixed into Rubrene thin films with different proportions to fabricate a series of luminescent devices. By measuring the magneto-electroluminescence (MEL) and current-luminescence ($I$-$B$) curves of the devices under different temperatures and currents, we found that the MEL profiles of light-emitting devices with different mixing ratios at room temperature show an STT fingerprint characteristic curve of magnetic field modulation. MEL amplitude first increases and then decreases with increased mixing ratio, whereas luminescence intensity increases monotonously. This is different from conventional Rubrene doped devices (such as mCP: $y$%Rubrene) which show STT increases with increasing concentration but with decreasing luminescence . By analyzing the singlet and triplet energy levels and emission spectra of Ir(ppy)$_{3}$ and absorption spectra of Rubrene, it can be seen that aside from Rubrenes molecular spaces influence on the STT process, intersystem crossing (ISC) caused by the strong SOC of Ir(ppy)$_{3}$ and energy transfer processes between the T$_{1}$ exciton of Ir(ppy)$_{3}$ and the S$_{1}$ exciton of Rubrene are also included in the devices. The combined action of these three micro-mechanisms leads complex MEL and luminescence changes in the device, and the devices current density and working temperature also have a good regulatory effect on them. Obviously, this study helps with understanding of the microscopic process and its evolution mechanism based on Rubrene optoelectronic devices.

Diffuse reflectance behavior of the printed cotton/nylon blend fabrics treated with zirconium and cerium dioxide and citric acid in near‐ and short‐wave IR radiation spectral ranges

AbstractNear‐ and short‐wave IR emission spectra of printed cotton/nylon blend fabrics coated with inorganic compounds in order to tune their diffuse reflectance behavior to the ones with woodland and desert backgrounds are investigated. In this regard, cotton/nylon blend fabrics printed with a four‐color digital pattern were used as the substrate, and different concentrations of zirconium and cerium dioxide (ZrO2 and CeO2) with and without citric acid as a cross‐linker were loaded on these fabrics using the pad‐dry‐cure method. The diffuse reflectance of the coated fabrics with various concentrations of nanoparticles and a cross‐linker was first measured by near‐infrared (NIR) diffuse reflectance spectroscopy (DRS). Then, fabrics with an optimum concentration of nanoparticles and appropriate reflectivity profiles similar to woodland and desert were investigated by field emission scanning electron microscopy (FE‐SEM), energy‐dispersive spectroscopy (EDS), washing, and rubbing fastness properties. In general, NIR and short‐wave infrared (SWIR) reflectance of fabrics coated with ZrO2 and CeO2 nanoparticles in range of 1% to 1.5% (w/v [%]) was suitable for matching with different environments. According to the findings obtained from the durability test, it was concluded that the washing fastness of the treated fabrics with CeO2 nanoparticles was excellent in both environments. FE‐SEM images of the treated fabrics containing ZrO2 and CeO2 indicated that the presence of nanoparticles on the surface of fabrics in woodland patterns was greater than the desert ones. However, the coated fabrics with CeO2 and citric acid in the woodland pattern have shown better dispersion with a mean particle size of 30 to 60 nm.

Theoretical Design of Near-Infrared Fluorescent Sensor for F Anion Detection Based on 10-Hydroxybenzo[h]quinoline Backbone.

Proper design and development of near-infrared (NIR) fluorescent sensors is very important for applications in vivo. In this work, we theoretically designed a ratiometric and NIR fluorescent sensor based on the 10-hydroxybenzo[h]quinoline (HBQ) backbone via systematically investigating the substituent effects of electron-donating groups (−NH2, −CH3, −C(CH3)3) and electron-withdrawing groups (−NO2, −CN, −F, −Cl, −CF3) at the proton donor site on the proton transfer process in HBQ in both the S0 and the S1 states. According to the calculated potential energy profiles along the proton transfer as well as the photophysical properties among all the derivatives, we successfully screened out that 7NH2-HBQ is a promising fluorescent sensor exhibiting the near IR emission spectra accompanied by the large Stokes shift. The potential use of 7NH2-HBQ for F– detection among anions (F–, Cl–, and Br–) was further studied, and the results showed that 7NH2-HBQ is very sensitive and selective toward F– based on the intermolecular hydrogen bonding interaction between F– and OH bond, forming a new complex FACS0. The ratiometric change in the fluorescence intensity could be induced by the H–F bond transfer from the O atom to the N atom in the S1 state.

Quantitative evaluation of the transmission spectrum in ophthalmic lenses

This paper presents the analysis of the transmission spectrum in four commercial ophthalmic lenses (offered by the company “LensBest”) with different technological characteristics. To evaluate the transmission bandwidth, an experimental setup wich consists on a light source, based on an MSR700 bulb, and was implemented, which provides a UV, visible and near IR emission spectrum. A spectrophotometer was assembled with a Newport monochromator and its corresponding instrumentation. The measurement system was characterized by a sodium discharged lamp, after which a reference measurement of the light source emission was taken. Next, each of the ophthalmic lenses was placed as a sample, with the emission spectrum of the light source and the transmission spectrum of each lens, the comparison in transmission of each element was made. This work allowed us to verify the functionality of each product, as well as validate the characteristics reported by the manufacturer.

Laboratory experiments on cosmic dust and ices

AbstractThe existence of cosmic dust is attested by the interstellar extinction and polarization, IR emission and absorption spectra, and elemental depletion patterns. Dust grains are efficiently processed or even destroyed in shocks, molecular clouds, or protoplanetary disks. A considerable amount of dust has to be re-formed in the ISM. In various astrophysical environments, dust grains are covered by molecular ices and therefore contribute or catalytically influence the chemical reactions in these layers. Laboratory experiments are desperately required to understand the evolution of grains and grain/ice mixtures in molecular clouds and early planetary disks. This review considers recent progress in laboratory approaches to dust/ice experiments.

UV Photolysis of Pyrazine and the Production of Hydrogen Isocyanide.

Photolysis of the diazine heterocycle, pyrazine, following irradiation at 308, 248, and 193 nm was examined using nanosecond time-resolved Fourier transform infrared emission spectroscopy. The resulting time-resolved IR emission spectra reveal that for 308 and 248 nm vibrationally highly excited pyrazine is produced, but no photolysis products were detected. However, at 193 nm excitation, the measured IR emission spectra consist solely of resonances originating from rovibrationally excited photofragments, including acetylene (HCCH), hydrogen cyanide (HCN), and hydrogen isocyanide (HNC), indicating that photofragmentation proceeds from vibrationally highly excited pyrazine on the ground electronic state. Spectral fit analysis of the time-resolved HCN and HNC IR emission band shapes and intensities allowed an estimate of the nascent product population distributions, from which a lower bound estimate of the HNC/HCN branching ratio was deduced as Φ ≥ 0.07. Additionally, ab initio calculations were performed in order to examine the propensity of photoinduced reactions on the ground- and lowest-energy excited-state surfaces. The calculations provide a basis for understanding the wavelength dependence of the UV photolysis of pyrazine, the photolytic production of HNC, and also explain previous experimental observations in the literature.

IR Emission of Single-Crystal Silicon Excited by Broadband Light

Room-temperature mid-IR emission from single-crystal silicon exposed to broadband (320 to 700 nm) light with power up to 150 m W has been revealed by Fourier transform IR emission spectroscopy. It is shown that broadband optical excitation significantly enhances IR emission in comparison with thermal emission. Spectral lines of lattice vibrations caused by interaction between combinations of longitudinal and transverse optical or acoustic phonons are identified in experimental IR emission spectra.

Investigation of near-infrared luminescence in Er3+ and Er3+/Yb3+ co-doped ZnMgAl10O17 phosphors

ZnMgAl10O17-phosphor samples doped with Er3+ ions and codoped with both Er3+ and Yb3+ ions were prepared using a combustion method. The formation of combustion products was confirmed by the XRD analysis. Upon the excitation at 980 nm, the IR-emission spectra of ∼1.53 μm were measured for the Er3+-doped and Er3+/Yb3+-codoped ZnMgAl10O17-phosphor samples. The deconvolvement of the emission spectra and the fitting analysis suggest that the Er3+ ions occupied the same sites in both phosphor samples. Further, the wavelength of the sublevel-split components and the effective linewidths were determined. The significant enhancement of the IR-emission intensity and the broadening of the Er3+ ions (4I13/2 → 4I15/2) in the prepared phosphors were explored.

The Influence of Metal Ion Binding on the IR Spectra of Nitrogen-Containing PAHs.

Astronomical IR emission spectra form the basis for the now widely accepted abundant presence of polycyclic aromatic hydrocarbons (PAHs) in inter- and circumstellar environments. A small but consistent frequency mismatch is found between the astronomically observed emission band near 6.2 μm and typical CC-stretching vibrations of PAHs measured in laboratory spectra near 6.3-6.4 μm. The shift of the band has been tentatively attributed to a variety of effects, among which the inclusion of heteroatoms, in particular nitrogen, in the PAH skeleton (PANH) as well as to metal ion binding to the PAH molecule. Here we experimentally investigate the combined effect of nitrogen-inclusion and metal ion binding on the IR spectra. In particular, infrared multiple-photon dissociation (IRMPD) spectra are recorded for coordination complexes of Cu+ with one or two quinoline, isoquinoline, and acridine ligands; complexes of the form Cu+(PANH) (MeCN), where the MeCN (acetonitrile) ligand acts as a relatively weakly bound "messenger" are also recorded to qualitatively verify that potential frequency shifts induced by IRMPD are minimal. The experimental IR spectra document the accuracy of IR spectral predictions by density functional theory calculations performed at the B3LYP/6-311+G(2df,2p) level and confirm that a σ-bond is formed between the copper ion and the exoskeletal N atom. The experimental spectra suggest that the CNC stretching mode undergoes a small red shift of up to 20 cm-1, with respect to the band position in the uncomplexed PANH molecule, away from the 6.2 μm interstellar position.

Shortening Response Time of Light-Emitting Electrochemical Cell By Addition of Ionic Liquid into Iridium Complex Film

Light-emitting electrochemical cells (LECs) are single layer electroluminescent devices consisting of a luminescent material. A large number of LECs using Iridium(Ⅲ) as the metal core to emit various color variations have been evaluated recently. However, there are many problems about performance or stability. We have aimed the improvement of the performance and stability of LECs using Ir complex. So, we have synthesized yellow emission ionic transition-metal complex, Ir(ppy)2(dtbbpy)NTf2. The resulting product is confirmed by 1H NMR. The absorption and emission spectra of Ir(ppy)2(dtbbpy)NTf2 in acetonitrile solution at room temperature were measured. The absorption bands were observed in the range of 230-350 nm assigned to spin-allowed π-π* and in the range of 350-500 nm assigned to spin-forbidden MLCT, LLCT, LC transitions. The emission peak was observed at 558 nm using an excitation wavelength of 420 nm. The redox behavior was characterized by cyclic voltammetry. We fabricated light-emitting electrochemical cell using Ir(ppy)2(dtbbpy)NTf2. Electrogenerated chemiluminescence peak was observed at 556nm indicating yellow emission. Addition of ionic liquid, (1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide) into Ir(ppy)2(dtbbpy)NTf2 film in the mixing weight ratio of 4:1 makes response time decreased dramatically. And electroluminescence layer thickness was controlled by adjusting the concentration of Ir(ppy)2(dtbbpy)NTf2 in acetonitrile solution to shorten response time.

Possibility of Light-Induced Mid-IR Emission in Situ Analysis of Plants

We perform the spectral analysis of fresh leaves using light-induced mid-IR emission spectroscopy (LIMIRES), a technique utilizing CW optical pumping for preparing and monitoring vibrationally excited states of chromophores. We show how to obtain high-quality IR-emission spectra of intact leaves using visible light of low intensity and sensitive Fourier transform infrared spectroscopy (FTIR). Changing the conditions of illumination, we carry out the spectral discrimination between leaf samples of wild plants and transgenic tobacco plants. Our results show that LIMIRES is a valuable new technique for studying the vibrational structure of excited pigments as well as the nondestructive monitoring of the quality of tobacco leaves.