Infrared Emission Bands Research Articles

Detection of interstellar 1-cyanopyrene: A four-ring polycyclic aromatic hydrocarbon

Polycyclic aromatic hydrocarbons (PAHs) are organic molecules containing adjacent aromatic rings. Infrared emission bands show that PAHs are abundant in space, but only a few specific PAHs have been detected in the interstellar medium. We detect 1-cyanopyrene, a cyano-substituted derivative of the related four-ring PAH pyrene, in radio observations of the dense cloud TMC-1 using the Green Bank Telescope. The measured column density of 1-cyanopyrene is ∼ 1 .52×10 12 cm − 2 , from which we estimate that pyrene contains up to 0.1% of the carbon in TMC-1. This abundance indicates that interstellar PAH chemistry favors the production of pyrene. We suggest that some of the carbon supplied to young planetary systems is carried by PAHs that originate in cold molecular clouds.

Synthesis of Organic and Inorganic Compounds in Asymptotic Giant Branch Stars

After the synthesis of carbon in the core of asymptotic giant branch (AGB) stars, carbon is dredged up to the surface by convection. Many carbon-based molecules are formed in the subsequently developed stellar wind. These include acetylene, which can link together to form benzene in post-AGB evolution. The emergence of the spectral signatures of aromatic and aliphatic compounds in the transition phase between AGB stars and planetary nebulae suggests that complex organic compounds can be formed in the circumstellar environment over very short (103 yr) timescales. We suggest that the carrier of the family of unidentified infrared emission bands is an amorphous carbonaceous compound—mixed aromatic/aliphatic nanoparticles (MAONs). The implications of the synthesis of complex organics in evolved stars are discussed.

Visible to infrared wide wavelength range luminescence of Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphor under 808/980 nm excitation and temperature sensing application

Here, the Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphors are prepared through solid-state route. The upconversion (UC)/downshifting (DS) luminescence and temperature performances of all samples are investigated in detail. Under 808 nm excitation, the infrared emission band (∼2000 nm) of Ho3+ ions is obtained. Especially, the energy transfer process of Nd3+ → Yb3+ → Ho3+ has increased the emission intensity of ∼2000 nm. Moreover, the infrared emission band presents thermal enhancement. Under 980 nm excitation, the UC emission band 500–960 nm is investigated. The green and red light of Ho3+ ion, near infrared light of Nd3+ ions are achieved. In addition, the possible luminescence mechanism of Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphor is discussed. At last, the optical temperature sensing characteristics of the phosphor are studied according to the luminescence intensity ratio (LIR) technology. The maximum relative sensitivity of Sr2LaNbO6: Yb3+/Nd3+/Ho3+ reaches 5.476 % K−1 at 293 K. These results prove that the Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphor presents the luminescence in infrared and visible range. The Sr2LaNbO6:Yb3+/Nd3+/Ho3+ phosphor also can be applied to design optical temperature sensor.

Infrared Spectrum of the Pyrene Anion in the CH Stretching Region.

In this work, we report the infrared spectrum of the pyrene anion, measured using messenger tagging with up to three Ar atoms. We assign the spectrum using density functional theory and vibrational perturbation theory. We discuss our results in the context of computed and experimental spectra from the literature as well as recent observations from astronomical sources, addressing the question of whether polycyclic aromatic hydrocarbon anions could contribute to the strong infrared emission bands at 3.29 μm from carbon-rich regions of space.

Complex Organics in Space: A Changing View of the Cosmos

Planetary explorations have revealed that complex organics are widely present in the solar system. Astronomical infrared spectroscopic observations have discovered that complex organics are synthesized in large quantities in planetary nebulae and distributed throughout the galaxy. Signatures of organics have been found in distant galaxies, as early as 1.5 billion years after the Big Bang. A number of unsolved spectral phenomena such as diffuse interstellar bands, extended red emissions, 220 nm feature, and unidentified infrared emission bands are likely to originate from organics. In this paper, we discuss the possible chemical structures of the carriers of these unexplained phenomena, and how these organics are synthesized abiotically in the universe. We raise the possibility that the primordial solar system was enriched by complex organics synthesized and ejected by evolved stars. The implications of possible stellar organics in primordial Earth are also discussed.

Luminescent thermometry with YVO4:Er/Nd: Achieving high sensitivities within the 1st and 2nd biological windows

YVO4:Er3+, Nd3+ powders were prepared by the modified sol gel synthesis route using glucose as chelating agent and characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM). Under 660 nm excitation, four infrared emission bands located between 790 and 845 nm, 870 and 930 nm, 950 and 1030 nm, and between 1050 and 1100 nm were observed, and were assigned the transitions 4F5/2 – 4I9/2 (Nd) and 4I9/2 – 4I15/2 (Er), 4F3/2 – 4I9/2 (Nd), 4I11/2 – 4I15/2 (Er), and 4F3/2 – 4I11/2 (Nd), respectively. The performance of these powders as optical temperature sensors using the luminescence intensity ratio (LIR) technique between thermally coupled levels (TCLs) and non-thermally coupled levels (non-TCLs) was studied within the temperature range of 293–373 K. Using different combinations of the emission intensities at 809, 880, 914 and 1003 nm, three distinct (LIR) temperature sensors schemes were built, with both excitation and emission within the first and second biological window. These LIRs relative sensitivity (Sr) and temperature uncertainties (δT) were investigated for samples with different Er and Nd concentrations. Sr values up to 2.08 ± 0.03%. K−1 and δT smaller than 1 K, were obtained. Repeatability and reproducibility tests demonstrated the reliability of the proposed LIRs.

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.

Broadband near infrared emission in Cr3+: Cs2AgBiCl6 double perovskite halides

Near Infra-red phosphors with broad emission band, high thermal stability and excellent efficiency are required in various bioimaging applications. In this study, we report the design and chemical reflux synthesis of a new family of Cr3+: Cs2AgBiCl6 double perovskites. In detail this article focuses on the impact of Cr3+ doping on the crystal structure, optical and vibrational properties of Cs2AgBiCl6 double perovskites. Different concentrations of Cr3+ doped Cs2AgBiCl6 double perovskites were analyzed using UV–Visible, Raman, Photoluminescence (PL), PL excitation, time resolved PL, X-ray photoelectron spectroscopy. Morphological analyses were carried out using scanning and transmission electron microscopies. XRD spectra reveals that the cubic symmetry remains unaltered upon Cr3+ doping. Raman and Rietveld analysis show that the Bi–Cl bond decreases upon Cr3+ incorporation. Optical absorption studies reveal a decrease in bandgap from 2.76 to 2.66 eV upon Cr3+ doping. PL spectroscopy of Cr 3+:Cs2AgBiCl6 exhibits a broad near infrared (NIR) emission band at 973 nm with an FWHM of 186 nm at 355 nm excitation. This demonstrates the promising prospects for NIR light emitting diode and bioimaging applications of Cr3+:Cs2AgBiCl6 double perovskites.

Blue/NIR-emitting Phosphor Based on Sr2CeO4: Tm3+, Yb3+ Obtained by Combustion Synthesis

In this study, pure Sr2CeO4 (SCO) and codoped Sr2CeO4:Tm3+, Yb3+ (SCO:Tm, Yb) of powder phosphors were synthesized by a combustion technique. The concentration of Tm3+ was fixed at 0.5 mol %, while the Yb3+ doping concentration was varied from 0 to 7.0 mol %. The crystalline structure, morphology and luminescence properties were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectroscopy, respectively. The XRD analysis shows the crystalline orthorhombic phase for all synthesized samples of SCO and SCO: Tm, Yb. The SEM results show that the doped sample with 5.0 mol % Yb3+ has the lowest grain particle size of 1.92 mm. The SCO:Tm, Yb phosphors produce mainly blue and near infrared emission bands centered at 481 nm and 813 nm (under 980 nm, excitation) which corresponds respectively to 1G4→3H6 and 3H4→3H6 transitions of Tm3+. In addition, the international commission on illumination CIE coordinates were calculated for all samples taking the range of 400 – 700 nm obtaining for the 5.0 mol % Tm3+ doped sample the coordinates: (x,y) = (0.0833, 0.1671) which match with pure blue color. Due to the strong blue and near infrared emissions, the SCO:Tm, Yb phosphors could be good candidates for use in biomarkers or lighting applications.

Buckyball-metal Complexes as Potential Carriers of Astronomical Unidentified Infrared Emission Bands

Efforts over 40 yr still leave the source of astronomical infrared emission bands largely unidentified. Here, we report the first laboratory infrared (6–25 μm) spectra of gas-phase fullerene-metal complexes, [C60-Metal]+ (Metal = Fe, V) and show with density functional theory calculations that complexes of C60 with cosmically abundant metals, including Li, Na, K, Mg, Ca, Al, V, and Fe, all have similar spectral patterns. Comparison with observational infrared spectra from several fullerene-rich planetary nebulae demonstrates a strong positive linear cross-correlation. The infrared features of [C60-Metal]+ coincide with four bands attributed earlier to neutral C60 bands and in addition also with several bands unexplained to date. Abundance and collision theory estimates indicate that [C60-Metal]+ could plausibly form and survive in astrophysical environments. Hence, [C60-Metal]+ are proposed as promising carriers, in supplement to C60, of observational bands, potentially representing the largest molecular species in space other than C60, C60 +, and C70.

Dust properties around NGC 7023 nebula in interstellar medium using IRIS, AKARI, and WISE survery


 
 
 
 We have studied the physical properties of dust around the nebula NGC 7023. The physical properties have been studied at 60 μm and 100 μm in the IRIS survey, 90 μm and 140 μm in the AKARI survey, and 12 μm and 22 μm in the WISE survey at the right ascension (R.A.) (J2000) = 21h01m35.60s, declination (J2000) = + 68o10m10.0s. The nebula is found at a distance of 335.82 pc from us. We found the dust color temperature is in the range between 36.19 K ± 0.03 K to 24.49 K ± 0.03 K with an average dust color temperature of 28.24 K ± 0.03 K in IRIS survey and a range between 38.80 K ± 0.25 K to 21.00 K ± 0.25 K with an average dust color temperature 26.39 K ± 0.25 K in AKARI survey. Similarly, in WISE, the dust color temperature was found in the range between 130.92 K ± 0.01 K to 88.71 K ± 0.01 K with an average of 104.76 K ± 0.25 K. The temperature in WISE is higher than that of the IRIS and AKARI survey. We have also calculated the dust mass, whose average value was found to be 1.18 x 1027 kg (5.93 x 10−4 M⊙) in IRIS, 1.06 x 1028 kg (5.33 x 10−3 M⊙) in AKARI, and 1.06 x 1027 kg (5.33 x 10−4 M⊙) in the WISE survey. We have also studied the visual extinction parameter due to such dust in infrared bands. This work will contribute to understanding infrared band emission from the dusty region around the nebular structure in the interstellar medium.
 
 
 

Broadband-sensitive up-conversion in Ni2+/Er3+ co-doped Gd2MgTiO6

Ni2+ doped and Ni2+/Er3+ co-doped Gd2MgTiO6 (GMT) phosphors have been synthesized by conventional high-temperature solid-state reaction method. First-principles calculation and X-ray diffraction analysis proves that Ni2+ ions occupy the Mg2+ sites in the Gd2MgTiO6 matrix at low Ni2+ doping concentration and begin to occupy Ti4+ sites at high Ni2+ doping concentration. The near infrared emissions of Ni2+ ions occupying Mg2+ and Ti4+ sites peak at 1344 nm and 1412 nm, respectively, forming a broad near infrared emission band from 1100 nm to 1700 nm. It is found that Ni2+/Er3+ co-doped Gd2MgTiO6 phosphor is capable to up-convert near infrared photons in the wavelength range of 870–1700 nm to visible 532 nm, 555 nm and 666 nm emission, caused by the energy transfer sensitization process from Ni2+ to Er3+. The Ni2+ and Er3+ concentration dependent up-conversion properties have been investigated and it is found that the Gd2MgTiO6: 2%Ni2+/5%Er3+ phosphor shows the strongest up-conversion emission, in which the energy transfer efficiencies from the Ni2+ ions occupying Mg2+ and Ti4+ sites to the Er3+ ions are 81.5% and 79.3%, respectively. The Gd2MgTiO6: 2%Ni2+/5%Er3+ phosphor shows yellow emission under the irradiation of 1342 nm and 1550 nm lasers, and green and orange-red emissions under the irradiation of 980 nm and 1064 nm laser, respectively. The broad band excitability and multi-color up-conversion performance of the Ni2+/Er3+ co-doped Gd2MgTiO6 phosphor suggest that it has wide application prospect in anti-counterfeiting, solar cell efficiency enhancement, infrared detection and so on.

Infrared spectra of isoquinolinium (iso-C9H7NH+) and isoquinolinyl radicals (iso-C9H7NH and 1-, 3-, 4-, 5-, 6-, 7- and 8-iso-HC9H7N) isolated in solid para-hydrogen.

Protonated polycyclic aromatic nitrogen heterocycles (H+PANH) are prospective candidates that may contribute to interstellar unidentified infrared (UIR) emission bands because protonation enhances the relative intensities of the bands near 6.2, 7.7 and 8.6 μm, and the presence of the N atom induces a blue shift of the ring-stretching modes so that the spectra of H+PANH match better with the 6.2 μm feature in class-A UIR spectra. We report the infrared (IR) spectra of protonated isoquinoline (the 2-isoquinolinium cation, iso-C9H7NH+), its neutral counterpart (the 2-isoquinolinyl radical, iso-C9H7NH), and another mono-hydrogenated product (the 6-isoquinolinyl radical, 6-iso-HC9H7N), produced on the electron-bombardment of a mixture of isoquinoline (iso-C9H7N) with excess para-hydrogen (p-H2) during matrix deposition at 3.2 K. To generate additional isomers of hydrogenated isoquinoline, we irradiated iso-C9H7N/Cl2/p-H2 matrices at 365 nm to generate Cl atoms, followed by IR irradiation to generate H atoms via Cl + H2 (v = 1) → HCl + H; the H atoms thus generated reacted with iso-C9H7N. In addition to iso-C9H7NH and 6-iso-HC9H7N observed in the electron-bombardment experiments, we identified six additional hydrogenated isoquinoline species, 1-, 3-, 4-, 5-, 7- and 8-iso-HC9H7N, via their IR spectra; hydrogenation on the N atom and all available carbon atoms except for the two sharing carbon atoms on the fused ring was observed. Spectral groupings were achieved according to their behaviors after maintenance of the matrix in darkness and on secondary photolysis at various wavelengths. The assignments were supported via comparison of the experimental results with the vibrational wavenumbers and IR intensities of possible isomers predicted using the B3LYP/6-311++G(d,p) method. The implications in the identification of the UIR band are discussed.

Optical Spectrum of the Diamantane Radical Cation

Similarities exist between the infrared spectra of diamondoids and unidentified infrared emission bands seen in the spectra of young stars with circumstellar disks. Due to their low ionization energy and absorption in the visible range, the radical cations of these highly stable molecules are also suggested to contribute to the well-known but largely unassigned diffuse interstellar bands. However, thus far only the optical spectrum of the adamantane cation (Ada+) has been measured in the laboratory, which is required for astronomical identification. Herein, we present the optical spectrum of the diamantane radical cation (C14H20 +, Dia+, D 3d) between 400 and 1000 nm in the gas phase. The spectra are obtained by electronic photodissociation (EPD) of mass-selected ions generated by electron ionization and trapping in a cryogenic trap at 5 K. The most intense fragmentation channels are the losses of H and C4H9. The optical spectrum reveals two broad and unresolved bands centered near 760 and 450 nm that are assigned to the D 2(2 E u) ← D 0(2 A 1g) and D 5(2 A 2u) ← D 0(2 A 1g) transitions using density functional theory. Despite a vibrational temperature below 20 K, no vibrational structure is resolved. Franck–Condon simulations of the D 5 ← D 0 transition predict intense vibronic progressions that become indiscernible from the band contour at spectral widths above 350 cm−1. Thus, the lack of resolved spectral features is attributed to lifetime broadening, Franck–Condon congestion arising from geometric changes, and possibly vibronic coupling. In addition to the EPD spectra, we characterize the ground state of Dia+ by analysis of a remeasured photoelectron spectrum and a predicted infrared spectrum.

Machine-learning identified molecular fragments of polycyclic aromatic hydrocarbons responsible for interstellar infrared emission bands

Machine-learning identified molecular fragments of polycyclic aromatic hydrocarbons responsible for interstellar infrared emission bands

Supporting Information for "Machine-learning identified molecular fragments of polycyclic aromatic hydrocarbons responsible for interstellar infrared emission bands"

Supporting Information for "Machine-learning identified molecular fragments of polycyclic aromatic hydrocarbons responsible for interstellar infrared emission bands"

Rotational and Vibrational Spectra of the Pyridyl Radicals: A Coupled-Cluster Study.

Pyridyl is a prototypical nitrogen-containing aromatic radical that may be a key intermediate in the formation of nitrogen-containing aromatic molecules under astrophysical conditions. On meteorites, a variety of complex molecules with nitrogen-containing rings have been detected with nonterrestrial isotopic abundances, and larger nitrogen-containing polycyclic aromatic hydrocarbons (PANHs) have been proposed to be responsible for certain unidentified infrared emission bands in the interstellar medium. In this work, the three isomers of pyridyl (2-, 3-, and 4-pyridyl) have been investigated with coupled cluster methods. For each species, structures were optimized at the CCSD(T)/cc-pwCVTZ level of theory and force fields were calculated at the CCSD(T)/ANO0 level of theory. Second-order vibrational perturbation theory (VPT2) was used to derive anharmonic vibrational frequencies and vibrationally corrected rotational constants, and resonances among vibrational states below 3500 cm-1 were treated variationally with the VPT2+K method. The results yield a complete set of spectroscopic parameters needed to simulate the pure rotational spectrum of each isomer, including electron-spin, spin-spin, and nuclear hyperfine interactions, and the calculated hyperfine parameters agree well with the limited available data from electron paramagnetic resonance spectroscopy. For the handful of experimentally measured vibrational frequencies determined from photoelectron spectroscopy and matrix isolation spectroscopy, the typical agreement is comparable to experimental uncertainty. The predicted parameters for rotational spectroscopy reported here can guide new experimental investigations into the yet-unobserved rotational spectra of these radicals.

Infrared Spectra of 1-Quinolinium (C9H7NH+) Cation and Quinolinyl Radicals (C9H7NH and 3-, 4-, 7-, and 8-HC9H7N) Isolated in Solid para-Hydrogen.

Large protonated polycyclic aromatic hydrocarbons (H+PAH) and the corresponding nitrogen heterocycles (H+PANH) have been proposed as possible carriers of unidentified infrared (UIR) emission bands from galactic objects. The nitrogen atom in H+PANH is expected to induce a blue shift of the band associated with the CC-stretching mode of H+PAH near 6.3 μm so that their emission bands might agree better with the UIR band near 6.2 μm. We report the IR spectrum of protonated quinoline (1-quinolinium cation, C9H7NH+) and its neutral species (1-quinolinyl radical, C9H7NH) measured upon electron bombardment during the deposition of a mixture of quinoline (C9H7N) and para-hydrogen (p-H2) at 3.2 K, indicating that the protonation and hydrogenation occur mainly at the N atom site. Additional experiments on the irradiation of C9H7N/Cl2/p-H2 matrices at 365 nm to generate Cl atoms, followed by irradiation with IR light to generate H atoms via Cl + H2 (v = 1), were performed to induce the reaction H + C9H7N. This method proved to be efficient for hydrogenation reactions in solid p-H2; we identified, in addition to C9H7NH observed in electron-bombardment experiments, four radicals with hydrogenation at the C-atom site─3-, 4-, 7-, and 8-HC9H7N. Spectral assignments were achieved according to the behavior upon secondary photolysis and a comparison of experimental results with vibrational wavenumbers and IR intensities predicted with the B3LYP/6-311++G(d,p) method. The observed lines at 1641.4, 1598.4, and 1562.0 cm-1 associated with the CC-stretching mode of C9H7NH+ are blue-shifted from those at 1618.7, 1580.8, 1556.7, and 1510.0 cm-1 of the corresponding protonated naphthalene (C10H9+).

Enhancing of the blue/NIR emission of novel BaLaAlO4:Yb3+(X mol%),Tm3+ (0.5 mol%) upconversion phosphors with the Yb3+ concentration (X = 0.5 to 6)

We report the structural, morphological and luminescent properties of the BaLaAlO4:Yb3+,Tm3+ (BAL:Yb,Tm) phosphors synthesized by a combustion method. The concentration of Tm3+ was fixed at 0.5 mol%, while that of Yb3+ was varied from 0 to 7 mol%. The X-ray diffraction patterns demonstrated that the samples synthesized with the Yb3+ co-dopant had an orthorhombic phase. In addition, the scanning electron microscopy images revealed that the BAL:Yb,Tm phosphors are formed by a mixture of coalesced microparticles with irregular shape and their surface is decorated with smaller nanoparticles. The size of these nanoparticles increases from 67 to 838 nm after increasing the Yb3+ concentration from 0 to 7 mol%. The BAL:Yb,Tm phosphors produced blue, red and Near infrared emission bands centered at 478, 658 and 800 nm (under 980 nm excitation), respectively. Moreover, the CIE (International commission on illumination) coordinates were calculated for all the samples and realized that they are always in the blue region of the CIE map. This suggests that the increase of the Yb3+ concentration in the BAL:Yb,Tm phosphors mainly favors the blue emission at 478 nm, since the red emission was always weak and contributed at most with ≈26% of the overall emission. Thus, the results of this work indicate that the BAL:Yb,Tm phosphors could be good candidates for their use in biomarkers or lighting applications.

Sensitization of Nd3+ Luminescence by Mn4+ in Mn4+, Nd3+ Codoped K0.5La0.5SrMgWO6

AbstractA series of Mn4+, Nd3+ codoped K0.5La0.5SrMgWO6 phosphors have been prepared by high‐temperature solid‐state reaction method. Under 468 nm excitation, near infrared emission bands centered at around 910 and 1064 nm are observed, assigned to the 4F3/2→4I9/2 and 4F3/2→4I11/2 transitions of Nd3+, respectively. The similarity between the excitation spectra in the 300–550 nm monitored at Mn4+ 697 nm emission and those monitored at Nd3+ 1064 nm emission as well as the lifetime shortening of Mn4+ emission with Nd3+ concentration increasing prove that the occurrence of the energy transfer sensitization from Mn4+ to Nd3+. In terms of the analysis results based on Dexter's theory and Inokuti‐Horayama model, it is believed that the dipole–dipole interaction plays a key role in the energy transfer process.