Spectrum Of Iodine Research Articles

Accurate calibration spectra for precision radial velocities

Astronomical spectrographs require calibration of their dispersion relation, for which external sources like hollow-cathode lamps or absorption-gas cells are useful. Laser frequency combs (LFCs) are often regarded as ideal calibrators because they provide the highest accuracy and dense sampling, but LFCs are facing operational challenges such as generating blue visual light or tunable offset frequencies. As an example of an external source, we aim to provide a precise and accurate frequency solution for the spectrum of molecular iodine absorption by referencing to an LFC that does not cover the same frequency range. We used a Fourier Transform Spectrometer (FTS) to produce a consistent frequency scale for the combined spectrum from an iodine absorption cell at 5200– 6200 Å and an LFC at 8200 Å. We used 17 807 comb lines to determine the FTS frequency offset and compared the calibrated iodine spectrum to a synthetic spectrum computed from a molecular potential model. In a single scan, the frequency offset was determined from the comb spectrum with an uncertainty of ∼1 cms−1. The distribution of comb line frequencies is consistent with no deviation from linearity. The iodine observation matches the model with an offset of smaller than the model uncertainties of ∼1 m s−1, which confirms that the FTS zero point is valid outside the range covered by the LFC, and that the frequencies of the iodine absorption model are accurate. We also report small systematic effects regarding the iodine model’s energy scale. We conclude that Fourier Transform Spectrometry can transfer LFC accuracy into frequency ranges not originally covered by the comb. This allows us to assign accurate frequency scales to the spectra of customized wavelength calibrators. The calibrators can be optimized for individual spectrograph designs regarding resolution and spectral bandwidth, and requirements on their long-term stability are relaxed because FTS monitoring can be performed during operation. This provides flexibility for the design and operation of calibration sources for high-precision Doppler experiments.

Artificial neural networks for laser frequency stabilization.

In order to stabilize a laser's emission frequency, absolute references such as molecular absorption lines are widely used. To automate the stabilization process, the desired absorption line needs to be identified reliably from a spectrum by a computer. We present an artificial neural network solving this task using the iodine spectrum as an example. The neural network is trained using only simulated data and subsequently tested using measured data. We show that this approach is robust against large variations of operating and environmental conditions.

Bisindole [3]arenes—Indolyl Macrocyclic Arenes Having Significant Iodine Capture Capacity

Bisindole [3]arenes—Indolyl Macrocyclic Arenes Having Significant Iodine Capture Capacity

Multistep Changes in Amyloid Structure Induced by Cross-Seeding on a Rugged Energy Landscape

Amyloid fibrils are aberrant protein aggregates associated with various amyloidoses and neurodegenerative diseases. It is recently indicated that structural diversity of amyloid fibrils often results in different pathological phenotypes, including cytotoxicity and infectivity. The diverse structures are predicted to propagate by seed-dependent growth, which is one of the characteristic properties of amyloid fibrils. However, much remains unknown regarding how exactly the amyloid structures are inherited to subsequent generations by seeding reaction. Here, we investigated the behaviors of self- and cross-seeding of amyloid fibrils of human and bovine insulin in terms of thioflavin T fluorescence, morphology, secondary structure, and iodine staining. Insulin amyloid fibrils exhibited different structures, depending on species, each of which replicated in self-seeding. In contrast, gradual structural changes were observed in cross-seeding, and a new type of amyloid structure with distinct morphology and cytotoxicity was formed when human insulin was seeded with bovine insulin seeds. Remarkably, iodine staining tracked changes in amyloid structure sensitively, and singular value decomposition analysis of the ultraviolet-visible absorption spectra of the fibril-bound iodine has revealed the presence of one or more intermediate metastable states during the structural changes. From these findings, we propose a propagation scheme with multistep structural changes in cross-seeding between two heterologous proteins, which is accounted for as a consequence of the rugged energy landscape of amyloid formation.

Calibrating Iodine Cells for Precise Radial Velocities

High fidelity iodine spectra provide the wavelength and instrument calibration needed to extract precise radial velocities (RVs) from stellar spectral observations taken through iodine cells. Such iodine spectra are usually taken by a Fourier Transform Spectrometer (FTS). In this work, we investigated the reason behind the discrepancy between two FTS spectra of the iodine cell used for precise RV work with the High Resolution Spectrograph (HRS) at the Hobby–Eberly Telescope (HET). We concluded that the discrepancy between the two HRS FTS spectra was due to temperature changes of the iodine cell. Our work demonstrated that the ultra-high resolution spectra taken by the TS12 arm of the Tull Spectrograph One at McDonald Observatory are of similar quality to the FTS spectra and thus can be used to validate the FTS spectra. Using the software IodineSpec5, which computes the iodine absorption lines at different temperatures, we concluded that the HET/HRS cell was most likely not at its nominal operating temperature of 70°C during its FTS scan at National Institute of Standards and Technology or at the TS12 measurement. We found that extremely high resolution echelle spectra (R > 200,000) can validate and diagnose deficiencies in FTS spectra. We also recommend best practices for temperature control and nightly calibration of iodine cells.

Hyperfine structure measurements of neutral atomic iodine (127I) in the infrared region (1800-6000 cm−1)

Experimental measurements of high resolution emission spectra of neutral atomic iodine (I I) have been extended to cover the mid-infrared spectral regions (1800–6000 cm−1) using Fourier transform spectroscopy. A total of 354 spectral lines are reported here in the above spectral range. While the region between 3000 and 6000 cm−1 were recorded using a conventional quartz Electrodeless Discharge lamps (EDL), spectra in the region 1800–3000 cm−1 were detected using specially prepared EDLs with a CaF2 window. Hyperfine structure analysis has been carried out on 224 spectral lines, of which 176 are reported for the first time. The magnetic dipole constant (A) and electric quadrupole constant (B) have been derived for 97 energy levels.

Deriving Iodine-free Spectra for High-resolution Echelle Spectrographs*

Abstract We describe a new method to derive clean, iodine-free spectra directly from observations acquired using high-resolution echelle spectrographs equipped with iodine cells. The main motivation to obtain iodine-free spectra is to use portions of the spectrum that are superimposed with the dense forest of iodine absorption lines, in order to retrieve lines that can be used to monitor the magnetic activity of the star, helping to validate candidate planets. In short, we provide a straightforward methodology to clean the spectra using the forward model used to derive radial velocities, the line spread function information plus the stellar spectrum without iodine to reconstruct and subtract the iodine spectrum from the observations. We show our results using observations of the star τ Ceti acquired with the Planet Finder Spectrograph (PFS), High Resolution Echelle Spectrometer (HIRES), and University College London Echelle Spectrograph (UCLES), reaching an iodine-free spectrum correction at the ∼1% rms level. We additionally discuss the limitations and further applications of the method.

Quantitative Analysis of Cartilage Invasion by Laryngeal Carcinoma with Dual-Energy CT Iodine Overlay Images and Spectrum Curve

Background: Laryngeal cancer stage is essential for determining the appropriate treatment strategies and evaluating prognosis for laryngeal carcinoma, which is based primarily on laryngeal cartilage invasion or not. However, there was no optimal means to confirm whether cartilage was being invaded before operation. With dual-energy CT development, it provided a new potential approach for laryngeal cartilage invasion diagnosis. Objectives: To evaluate the clinical value of dual-energy computed tomography with iodine overlay images and spectrum curve in the quantitative analysis of laryngeal cartilage invasion in patients with laryngeal carcinoma. Patients and Methods: Dual-source dual-energy CT was performed for one hundred and twenty patients with confirmed diagnosis of laryngeal carcinoma by surgical pathology (56 cases with laryngeal cartilage invasion and 64 cases without invasion). The mean CT attenuation values of laryngeal cartilage and the tumor in routine scan, arterial and venous phases was measured and cartilage invasion was considered to be present with asymmetric sclerotic changes, erosion, lysis and extralaryngeal tumor spread with iodine overlay images and routine scan images. Moreover, the sensitivity and specificity were analyzed. The slope of spectral curve and iodine concentration of the tumors, invaded laryngeal cartilage and non-invaded laryngeal cartilage were compared between arterial phase and venous phase. Furthermore, the receiver operating characteristic (ROC) curve of mean CT attenuation value, the slope of spectral curve and iodine concentration were made comparative analysis. Results: The mean CT attenuation values of the tumors, invaded laryngeal cartilage and non-invaded laryngeal cartilage had significant difference among the routine scan, arterial phase and venous phase (P < 0.05). The sign of asymmetric sclerotic changes had no significant difference between iodine overlay images and routine scan images (the same specificity and sensitivity, 77.8% and 52.6%, respectively). However, the signs of erosion, lysis and extralaryngeal tumor spread had significant difference. The specificity and sensitivity of iodine overlay images were superior to that of the routine scan images in the three signs (specificity and sensitivity of erosion: 92.3% vs. 61.5%, and 86.7% vs. 60.0%, respectively; lysis: 82.4% vs. 69.2%, and 81.8% vs. 66.7%, respectively; extralaryngeal tumor spread: 90.9% vs. 68.3%, and 100% vs. 63.5% respectively). The slope of spectral curve and iodine concentration of the tumors, invaded laryngeal cartilage and non-invaded laryngeal cartilage showed significant difference (P < 0.05). The iodine concentration of the tumor was higher than invaded laryngeal cartilage. The area under the curve (AUC) value of mean CT attenuation value in routine scan, arterial phase and venous phase were 0.064, 0.265, and 0.192, respectively. The AUC value of the slope of spectral curve in arterial phase was 0.970 and its selected cutoff was considered as 1.09. In this cutoff point, the diagnostic indices including sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 88.9%, 100%, 100%, and 82.6%, respectively, while the AUC value of the slope of spectral curve in venous phase was 0.944 and its selected cutoff was considered as 0.95. In this cutoff point, the diagnostic indices including sensitivity, specificity, PPV, NPV, positive likelihood ratio (PLR), negative likelihood ration (NLR) were 81.5%, 96.3%, 91.7%, 77.3%, 7.76, and 19.30, respectively. The AUC value of the slope of iodine concentration in arterial phase was 0.995 and its selected cutoff was considered as 1.05. In this cutoff point, the diagnostic indices including sensitivity, specificity, PPV and NPV were 92.6%, 100%, 95.8%, and 100%, respectively. Moreover, the AUC value of the slope of iodine concentration in venous phase was 0.905 and its selected cutoff was considered as 0.75. In this cutoff point, the diagnostic indices including sensitivity, specificity, PPV, NPV, PLR, and NLR were 77.8%, 88.9%, 91.3%, 82.6%, 7.00, and 24.5, respectively. Conclusion: Dual-energy CT can provided a new potential approach for laryngeal cartilage invasion diagnosis in order to guide the selection of optimal operation plan and improve the prognosis.

Revision of the ionization energy of neutral carbon

This publication describes a re-analysis of previously published data on neutral carbon (C I). We used critically examined and improved values for the line energies of the absorption spectrum of molecular iodine to calibrate the transition energies of C I absorption lines originating from the 1s22s22p3s 3P°2 level and terminating on highly excited Rydberg states of the 1s22s22pnp 3D3 series. This series converges on the first excited fine-structure level of the ionic ground configuration. Additional use of improved energy values for the 1s22s22p3s 3P°2 level and for the fine-structure interval of the ionic ground state together with modern fitting techniques lead to a new value of the ionization energy of neutral carbon with 9 times the precision of previous work, 90 820.348(9) cm−1 (equivalent to 11.260 2880(11) eV), as well as a table of predicted values for the energies of unobserved states in the series.

Radioactive iodine capture and storage from water using magnetite nanoparticles encapsulated in polypyrrole

The effective capture and storage of radioactive iodine is of importance for nuclear waste storage during nuclear power station accidents. Here we report Fe3O4@PPy powder containing ∼12nm magnetite (Fe3O4) nanoparticles encapsulated in the polypyrrole (PPy) matrix. It shows 1627mg/g uptake of iodine dissolved in water, within 2h at room temperature. Fe3O4@PPy is ferromagnetic in nature and can be separated from water using external magnetic field. The nitrogen gas sweeping test at 30°C shows release of 2% iodine from iodine adsorbed Fe3O4@PPy, revealing stable storage of iodine for a moderate period. The iodine-adsorbed magnetic powder can be regenerated by washing with ethanol. The XPS spectrum of iodine adsorbed Fe3O4@PPy confirmed the presence of polyiodides (I3− and I5−) bound to the PPy surface. This excellent iodine capture and storage from iodine contaminated water is an environment friendly, inexpensive and large scale method.

Surface‐Active Properties of Solvent‐Extracted Panax ginseng Saponin‐Based Surfactants

AbstractIn this study, saponins were extracted from Panax ginseng root powder. The crude solvent‐extracted saponins containing triterpenoid glycosides and terpenes that were identified by TLC techniques. The critical micelle concentrations (CMC) of the saponins were determined by measuring the change in (a) the UV‐visible spectrum of iodine due to the micelle‐iodine complexation, (b) the absorption intensity of aqueous alpha‐lipoic acid due to the micellar solubilization of the drug, and (c) the surface tension due to the abrupt change in the air/liquid interface saturation by surfactants monomers. The development of new absorption peak due to the micelle‐iodine complexation, enhancement in the absorbance due to the micelle‐solubilized lipoic acid, and displacement of monomer‐micelle equilibrium to micelle formation in higher monomer concentration region are some of the physicochemical properties in which CMC could be determined. We found a CMC of 0.009% w/v.

In situ optical studies of thermal stability of iodine-doped polyazomethine thin films

Chemical vapour deposition (CVD) method, via polycondensation reaction, is used to obtain poly(1,4-phenylene-methylidynitrilo-1,4-phenylenenitrilomethylidyne) (PPI) thin films. The iodine (I2) doping process of these films is observed in situ, by means of changes of the absorbance spectra. A distinct reduction of the energy gap, being a result of p-type doping, is connected with extracting electrons from π-conjugated system and formation of the polaron states inside the gap. On the basis of UV–Vis–NIR(T) experiments, the heat treatment effect on the absorption coefficient spectra of iodine doped PPI thin films is reported, as a new method, to estimate thermal stability and to obtain the border temperature of doped polymer films. Moreover it is demonstrated that the analysis of absorption bands (shape, level and position) and absorption edge parameters, such as the Urbach energy (EU) and the energy gap (EG) can be used to evaluate the changes of polymer chain conformation and conjugation.

Combining configuration interaction with perturbation theory for atoms with a large number of valence electrons

A version of the configuration interaction (CI) method is developed which treats highly excited many-electron basis states perturbatively, so that their inclusion does not affect the size of the CI matrix. This removes, at least in principle, the main limitation of the CI method in dealing with many-electron atoms or ions. We perform calculations of the spectra of iodine and its ions, tungsten, and ytterbium as examples of atoms with open $s$, $p$, $d$ and $f$-shells. Good agreement of the calculated data with experiment illustrates the power of the method. Its advantages and limitations are discussed.

Study of molecular iodine, iodate ions, iodide ions, and triiodide ions solutions absorption in the UV and visible light spectral bands

The paper reports on experimental studies concerning the absorption spectra of molecular iodine and its , I−, anions in the spectral band of 180–600 nm. Values of the absorption cross-sections of the above mentioned substances have been measured, and relations of absorption coefficients to concentrations have been studied. The results obtained demonstrate that the spectral band under consideration is likely to be successfully used for simultaneous real-time detection of substances containing iodine with an absorption method using laser emission sources in the UV and visible light spectral bands.

Hyperfine structure near infrared spectrum of atomic iodine

The hyperfine structure of spectral lines of neutral iodine (II) in the wavenumber region from 11300cm−1 to 13000cm−1 was studied using optical heterodyne concentration modulation absorption spectroscopy with a tunable single-mode cw Ti:Sapphire laser. The iodine atoms were produced and excited by a discharge operated in a mixture of helium and iodine vapor. A total of 89 lines were observed and the hyperfine structure of 45 of these lines was studied. For 40 lines, the hyperfine structure was not previously known. The magnetic dipole and the electric quadrupole hyperfine structure constants of 18 even and 28 odd levels were extracted. The constants of one even level and of 16 odd levels are presented for the first time.

Internal dosimetry through GATE simulations of preclinical radiotherapy using a melanin-targeting ligand

The GATE Monte Carlo simulation platform based on the Geant4 toolkit is under constant improvement for dosimetric calculations. In this study, we explore its use for the dosimetry of the preclinical targeted radiotherapy of melanoma using a new specific melanin-targeting radiotracer labeled with iodine 131. Calculated absorbed fractions and S values for spheres and murine models (digital and CT-scan-based mouse phantoms) are compared between GATE and EGSnrc Monte Carlo codes considering monoenergetic electrons and the detailed energy spectrum of iodine 131. The behavior of Geant4 standard and low energy models is also tested. Following the different authors’ guidelines concerning the parameterization of electron physics models, this study demonstrates an agreement of 1.2% and 1.5% with EGSnrc, respectively, for the calculation of S values for small spheres and mouse phantoms. S values calculated with GATE are then used to compute the dose distribution in organs of interest using the activity distribution in mouse phantoms. This study gives the dosimetric data required for the translation of the new treatment to the clinic.

Vibrational Spectrum of Iodine in the Visible Region: An Alternative to the Use of RAMAN Spectroscopy

Vibrational Spectrum of Iodine in the Visible Region: An Alternative to the Use of RAMAN Spectroscopy

Effect of iodine doping on the electrical transport mechanism in plasma polymerized 2,6-diethylaniline thin films

The current density–voltage characteristics of pure and iodine doped plasma polymerized 2,6-diethylaniline (PPDEA) thin films of different thicknesses ranging from 150 to 450nm with aluminum (Al)/PPDEA/Al structure have been investigated at room temperature. The direct current electrical conductivity has showed a higher value due to iodine doping of PPDEA thin film. In contrast to pure PPDEA thin films where the most probable conduction mechanism is electrode limited Schottky type, Poole–Frenkel (PF) conduction mechanism is found to be operative in iodine doped PPDEA thin films. The PF conduction mechanism in iodine doped PPDEA thin films may have generated due to the charge transfer complex formation through donor type monomer and acceptor type iodine. The presence of charge transfer complex is confirmed by a new absorption shoulder/peak in ultraviolet–visible spectrum of iodine doped PPDEA thin film.

Widely tunable laser frequency offset lock with 30 GHz range and 5 THz offset

We demonstrate a simple and versatile method to greatly extend the tuning range of optical frequency shifting devices, such as acousto-optic modulators (AOMs). We use this method to stabilize the frequency of a tunable narrow-band continuous-wave (CW) laser to a transmission maximum of an external Fabry-Perot interferometer (FPI) with a tunable frequency offset. This is achieved through a servo loop which contains an in-loop AOM for simple radiofrequency (RF) tuning of the optical frequency over the full 30 GHz mode-hop-free tuning range of the CW laser. By stabilizing the length of the FPI to a stabilized helium-neon (HeNe) laser (at 5 THz offset from the tunable laser) we simultaneously transfer the ~ 1 MHz absolute frequency stability of the HeNe laser to the entire 30 GHz range of the tunable laser. Thus, our method allows simple, wide-range, fast and reproducible optical frequency tuning and absolute optical frequency measurements through RF electronics, which is here demonstrated by repeatedly recording a 27-GHz-wide molecular iodine spectrum at scan rates up to 500 MHz/s. General technical aspects that determine the performance of the method are discussed in detail.

Adaptive dual-comb spectroscopy in the green region

Dual-comb spectroscopy is extended to the visible spectral range with two short-pulse frequency-doubled free-running ytterbium-doped fiber lasers. When the spectrum is shifted to other domains by nonlinear frequency conversion, tracking the relative fluctuations of the femtosecond oscillators at their fundamental wavelength automatically produces the correction signal needed for the recording of distortion-free spectra. The dense rovibronic spectrum of iodine around 19,240 cm(-1) is recorded within 12 ms at Doppler-limited resolution.