Transmission spectroscopy

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Transit timing variation and transmission spectroscopy analyses of the hot Neptune GJ3470b

Transit timing variation and transmission spectroscopy analyses of the hot Neptune GJ3470b

GJ3470b is a hot Neptune exoplanet orbiting an M dwarf and the first sub-Jovian planet to exhibit Rayleigh scattering. We present transit timing variation (TTV) and transmission spectroscopy analyses of multi-wavelength optical photometry from 2.4- m and 0.5-m telescopes at the Thai National Observatory, and the 0.6-m PROMPT-8 telescope in Chile. Our TTV analysis allows us to place an upper mass limit for a second planet in the system. The presence of a hot Jupiter with a period of less than 10 days or a planet with an orbital period between 2.5 and 4.0 days are excluded. Com- bined optical and near-infrared transmission spectroscopy favour an H/He dominated haze (mean molecular weight 1.08 ± 0.20) with high particle abundance at high alti- tude. We also argue that previous near-infrared data favour the presence of methane in the atmosphere of GJ3470b.
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Defocused transmission spectroscopy: a potential detection of sodium in the atmosphere of WASP-12b

Defocused transmission spectroscopy: a potential detection of sodium in the atmosphere of WASP-12b

associated with ground-based observations, the technique of transmission spectroscopy provides a unique challenge. How does one minimise the impact of systematics on observa- tions whilst searching for an extremely small signal? In a technique similar to defocussed photometry, we present the technique of ‘defocussed transmission spectroscopy’. As with defocussed photometry, the aim of defocussed spectroscopy is to spread the light over a larger number of pixels on the CCD in order to reduce flat-fielding errors, variations due to seeing, and other systematic sources of noise such as track- ing errors. In contrast to high-resolution transmission spec- troscopy, this method aims to maximise the signal-to-noise (SNR) achieved from the ground. Since we are attempting to characterise a strong individual spectral line, as opposed to the more subtle individual spectral features, our aim is sim- ply to maximise the SNR whilst using defocussing to min- imise systematics. This makes the technique ideal for less- bright targets that high-resolution spectroscopy has been unable to study in the past. In order to detect the hot- Jupiter atmospheric features, particular lines in the spec- trum are selected (e.g. Na), which are then compared to the surrounding continuum during transit. Any changes in the line depth due to the atmosphere annulus transiting the host star can then be detected by comparing the in- and out-of- transit line depths directly. This method can be applied to any ground-based set-up for both low- and high-resolution spectroscopy.
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Transmission spectroscopy of the inflated exoplanet WASP 52b, and evidence for a bright region on the stellar surface

Transmission spectroscopy of the inflated exoplanet WASP 52b, and evidence for a bright region on the stellar surface

Transmission spectroscopy using Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) was used to detect the first spectral feature of any exoplanet, that of the nar- row core of atomic sodium originating from the upper atmosphere of HD 209458b (Charbonneau et al. 2002). Broad-band opacity sources were later detected in this planet’s atmosphere in the form of the pressure broadened wings of Na I (Sing et al. 2008) and a blueward slope in the transmission spectrum interpreted as Rayleigh scattering by H 2 (Lecavelier Des Etangs et al. 2008b). This feature
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Rotation and Winds of Exoplanet HD 189733 b Measured with High-dispersion Transmission Spectroscopy

Rotation and Winds of Exoplanet HD 189733 b Measured with High-dispersion Transmission Spectroscopy

instead taken from Rothman et al. (1995). We de- scribed the terminator atmosphere of the planet by assuming an average temperature-pressure (T /p) profile. The lower part of the planet at- mosphere (p > 0.1 bar) cannot be probed by transmission spectroscopy. Any chosen T /p pro- file would essentially produce the same modeled transmission spectrum. Therefore, we chose to match the Madhusudhan & Seager (2009) profile, which is derived from secondary-eclipse measure- ment of the planet, with the simplest possible sam- pling. For p > 1 bar, an isothermal atmosphere at temperature 1750 K was adopted. Between 1 and 0.1 bar, temperature decreased to 1350 K. In the range −2.5 < log(p) < −1.0, we tested instead two opposite profiles, by making the tem- perature T 2 either increase to 1500 K or decrease
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Assessment of Azithromycin in Pharmaceutical  Formulation by Fourier-transform Infrared  (FT-IR) Transmission Spectroscopy

Assessment of Azithromycin in Pharmaceutical Formulation by Fourier-transform Infrared (FT-IR) Transmission Spectroscopy

bit less sensitivity for macrolides analysed in body fluids. Barrett et al. has used Tandem LC for quantification of azithromycin in plasma samples of human. Torano and Guchelaar have worked on a strategy using fluorescence detection for quantification of macrolide antibiotics in serum. Nirogi used solid-phase extraction then quantitative analysis was done on LC/MS/MS. The chromatographic techniques require huge amount of solvents, lengthy experimental procedures for sample clean-up, and also demand expensive equipment that might not be available in many laboratories [5-12]. The survey of published literature reveals that quantitative methods are meant for the measurement of azithromycin in bodily fluids like plasma, tissues etc and waste water. Detection is generally electrochemical, MS, UV and fluorescence after derivatization [13, 14]. Another popular method for quantitative analysis is FT-IR spectroscopy, which has proved to be a promising tool for the quantification of variety of samples. The NCEAC FT-IR group has credibly worked for development of new methods by applying FT-IR transmission spectroscopy to analyse various quality factors of oils and fat [15- 19]. FT-IR spectroscopy has previously been applied for quantification of azithromycin by dissolving it in toluene [20]. Electroanalytical techniques offer another possibility for estimating this compound due to a suitable electroactive site in its structure hence DPV method has also been applied [21]. The quality monitoring authorities in pharmaceutical industries need exact analysis of formulations produced so as to confirm that these contain the necessary quantity of the active component in order to follow good manufacturing practice (GMP) rules [22].
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Near Infrared Transmission Spectroscopy in the Food Industry

Near Infrared Transmission Spectroscopy in the Food Industry

Near Infrared Transmission Spectroscopy in the Food Industry Introduction: Near Infrared Spectroscopy is used in many industries including the pharmaceutical, petrochemical, agriculture, cosmetics, chemical and food industries. However in the food industry NIR has an almost universal application. Since food is made mostly from proteins, carbohydrates, fats and water, i.e. >99% by weight, NIR provides a means of measuring these components in almost any food.

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Optical transmission spectroscopy of hot Jupiter atmospheres

Optical transmission spectroscopy of hot Jupiter atmospheres

While the slopes seen in the optical transmission spectra of exoplanets are often interpreted as being caused by atmospheric opacity sources, it is also possible for activity on the host star to give rise to similar features. Star spots that are on the stellar surface but lie away from the transit chord (unocculted spots) make the star darker and redder which can lead to an overestimate of the planet’s size, making the transit depth larger towards bluer wavelengths. McCullough et al. (2014) re-analysed the Rayleigh scattering slope of HD 189733b presented in Pont et al. (2013) and found that unocculted star spots provided a comparable fit to the data. Similarly, Oshagh et al. (2014) found that plages (bright regions) on the stellar surface could also reproduce the Rayleigh scattering slope of HD 189733b if they were occulted during the planet’s transit. Occulted plages would cause dips in the transit light curve, getting larger towards bluer wavelengths, and cause a deeper transit to be observed than due to the planet’s atmosphere alone. These studies have prompted subsequent transmission spectroscopy studies to perform a careful analysis of the possible influences of stellar activity on their results. The results presented in this thesis also take this into consideration and this analysis is presented in Chapters 4, 5 and 6.
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Estimation of composition of quinoa (Chenopodium quinoa Willd.) grains by Near-Infrared Transmission spectroscopy

Estimation of composition of quinoa (Chenopodium quinoa Willd.) grains by Near-Infrared Transmission spectroscopy

provide rapid and accurate analysis of starch, moisture, protein, and oil contents in whole kernel cereals ( Büchman, Josefsson, & Cowe, 2001; Miralbes, 2004 ; and; Pojic, Mastilovic, Pestoric, & Radusin, 2008 ). However, when analysing intact samples by diffuse re flec- tance or transmittance spectroscopy, uncontrolled variations in light scattering are often a dominating artifact that complicates subsequent chemometric modelling ( Panero, Panero, Panero, & Silva, 2013 ). This undesired scattering variation is due to uncon- trolled physical variations of the samples, such as particle size and shape, sample packing, surface and orientation of the particles ( Cantor, Hoag, Ellison, Khan, & Lyon, 2011 ). In order to minimise the multiplicative interference of scatter and particle size for the con- struction of robust models, NIT spectra are subjected to processing techniques for signal correction (i.e., multiplicative scatter correc- tion and extended multiplicative signal correction) and noise
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Propagation of an electromagnetic wave in an absorbing anisotropic medium and infrared transmission spectroscopy of liquid crystals

Propagation of an electromagnetic wave in an absorbing anisotropic medium and infrared transmission spectroscopy of liquid crystals

Infrared absorbance spectroscopy is a powerful tech- nique for studying the molecular structure and this technique has also been applied to the study of liquid crystalline material 1 in the nematic phase since the early 1970’s. This technique was first applied in the early 1990’s to the study of the ferroelectric liquid crystalline materials and in particular for determining the tilt angle and the orientational order parameter. 2 Recently, the technique has been used to deter- mine a complete set of second rank orientational order parameters. 3,4 The orientational distribution function of the directors in smectic layers has been determined for the ferro- electric liquid crystals first by Fukuda et al. 5 In this paper we theoretically investigate the absorbance as a function of the angle of polarization where a ferroelectric liquid crystal is confined to lie between the two windows of a cell. The mea- surement of the absorption of infrared 共 IR 兲 radiation in a liquid crystal involves an arrangement shown schematically in Fig. 1. The radiation is divided by a beam splitter A; one part constituting a reference beam of intensity I ref , the other
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Infrared absorbance spectroscopy of aqueous proteins : comparison of transmission and ATR data collection and analysis for secondary structure fitting

Infrared absorbance spectroscopy of aqueous proteins : comparison of transmission and ATR data collection and analysis for secondary structure fitting

We have shown that ATR ‐ IR absorbance data of aqueous protein samples can be collected using a standard TGS detector and a ZnSe ATR unit. The data collection and baseline correction with ATR ‐ IR are much simpler than transmission spectroscopy in our hands. In ATR spectros- copy, the light intensity at the surface of the crystal depends on the refractive index, and hence absorbance, of the sample and in addition, the light intensity decays exponentially away from the surface in a manner that depends on the refractive index of the sample. We corrected for these effects by determining a wave num- ber – dependent correction factor for the ATR spectra. To implement this simply, we approximated our Kramers ‐ Krönig – determined refractive index of water as a sum of four linear components across the amides I and II regions of the spectrum and used this for the proteins and water in which they were dissolved to determine the wave num- ber – dependent correction factors. We simplified the cor- rection factor by using an ATR angle of incidence of 45°. We then normalized the resulting spectra and applied our self ‐ organizing map secondary structure fitting algorithm, SOMSpec, to the amide I data using the BioTools reference set to give secondary structure estimates. The resulting secondary structure estimates are encouraging for the future of ATR spectroscopy for this purpose. In our hands, the results were at least as good as those for our transmission data. For highly α‐ helical or β‐ strand proteins, the uncorrected ATR spectra can be used. For mixed structures, based on our experi- ence with lysozyme, the correction is necessary.
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Raman spectroscopy of graphite

Raman spectroscopy of graphite

In this paper we review the vibrational properties of graphite as measured by Raman spectroscopy. We first consider the symmetry of graphite, its phonon branches and Raman selection rules in § 2. Section 3 introduces the Raman spectra of graphite with emphasis on the disorder-induced modes and their overtones in the second- order spectrum. In particular, we describe the three key experiments that established the unusual properties of the disorder-induced bands experimentally. The theory of double-resonant Raman scattering is developed in § 4. We begin with the examples of two linear electronic bands, where the Raman cross-section can be calculated analytically. We then apply double-resonant Raman scattering to graphite and show that the peculiar excitation-energy dependence follows naturally from the double- resonant condition. The rest of § 4 treats the selection rules for double-resonant scattering, and the second-order and the anti-Stokes Raman spectra. Finally, we show in § 5 how to obtain the phonon dispersion from the disorder-induced and second-order Raman peaks in graphite. Section 6 summarizes this work.
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Hadron spectroscopy in LHCb

Hadron spectroscopy in LHCb

LHCb is a flavor factory, exploring a large set of physics topics. In particular, in the spectroscopy field, many new unexplored regions are being studied. These analyses are producing unexpected results, such as the discovery of “exotic” states, or the observation of many unexpected resonances and particles. Basic ingredients of these results are: the high statistics and purity of the final states and highly sophisticated and newly developed full amplitude analyses. This field is in rapid development and much more experimental and theoretical work is needed to understand the full pattern. Many more analyses are underway, making use of the large amount of data which are being collected at LHC.
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Hadron Spectroscopy at BESIII

Hadron Spectroscopy at BESIII

Abstract. The BESIII experiment, hosted at the IHEP of Beijing, has collected the world largest data sample in the charmonium energy region. One of the most important physics goals of BESIII is the investigation of the QCD prediction. QCD can be accessed in a unique way by means of hadron spectroscopy, which was extensively studied and many important progresses were achieved in the last years. Charmonium decays provide an excellent scenario for studying nucleons, hyperons and their excited states, XYZ reso- nances, as well as light hadrons. Some of the most recent results for hadron spectroscopy from BESIII will be reported.
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Meson spectroscopy at COMPASS

Meson spectroscopy at COMPASS

Abstract. The goal of the COMPASS experiment at CERN is to study the structure and dynamics of hadrons. The two-stage spectrometer used by the experiment has large acceptance and covers a wide kinematic range for charged as well as neutral particles and can therefore measure a wide range of reactions. The spectroscopy of light mesons is performed with negative (mostly π − ) and positive (p, π + ) hadron beams with a momentum of 190 GeV/c. The light-meson spectrum is measured in different final states produced in diffractive dissociation reactions with squared four-momentum transfer t to the target between 0.1 and 1.0 (GeV/c) 2 . The flagship channel is the π − π − π + final state, for which
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Multi-dimensional spectroscopy

Multi-dimensional spectroscopy

Experimentally the interactions and dynamics in complex systems manifest themself in various types of traditional one-dimensional spectroscopies (as Nuclear Magnetic Resonance (NMR), Infrared spectroscopy (IR), Raman spectroscopy etc.). Phenomena such as line broadening and spectral shifts of the spectra contain information on both the dynamics and intermolec- ular interactions. However, the information obtained in this way is not very clear, since different physical phenomena give rise to very similar effects in the observed response. More information can be obtained using multi-dimensional spectroscopies.
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Spectroscopy of baryon resonances

Spectroscopy of baryon resonances

scribed: Isgur and Karl demonstrated in their seminal pa- pers that the hyperfine interaction between quarks sug- gested in QCD can, without further free parameters, ex- plain the size and pattern of the splittings and the mixing angles observed experimentally in nonstrange, negative parity baryons [12]. The masses and mixing angles of the positive-parity baryons were also reasonably well repro- duced in their QCD-inspired model [13]. In short: meson and baryon spectroscopy seemed to be well understood, and QCD was considered to be the established theory of strong interactions, with no mysteries and nothing more to learn. A survey of results on QCD from high-energy ex- periments can be found in an article by S. Bethke, G. Dis- sertori, and G. P. Salam [15] in the Review of Particle Properties RPP [16].
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Nucleon Spectroscopy with CLAS

Nucleon Spectroscopy with CLAS

Identifying resonances and extracting resonance in- formation in partial-wave analyses (PWA) of experimental data is challenging and requires not only unpolarized cross-section data, but[r]

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POSITRON ANNIHILATION SPECTROSCOPY

POSITRON ANNIHILATION SPECTROSCOPY

2 This guess is significantly higher than the experimental observations of positron lifetimes in metals. The reason is in neglecting enhancement of the local electron density at the posi[r]

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Vibrational Raman Spectroscopy

Vibrational Raman Spectroscopy

Many common five-atom molecules have tetrahedral symmetry. According to Garland, et. al., 1 these molecules have four distinct normal modes of vibration that are all Raman active. With pure substances such as CCl 4 , it is usually possible to record Raman and IR spectra with sufficient sensitivity and resolution to observe and assign all four vibrational modes from either Stokes or anti-Stokes shifts. In general, we may use group theory to determine which modes of a given molecule are Raman and/or IR active. Consider tetrachloroethylene (C 2 Cl 4 ), which is a six-atom molecule. How many vibrational normal modes are there? What is its molecular point group? By analyzing the vibrational symmetry, it can be shown that the fundamentals are classified as follows: ν 1 ν 2 ν 3 (all A g ), ν 4 (A u ), ν 5 ν 6 (both B 1g ), ν 7 (B 1u ), ν 8 (B 2g ), ν 9 ν 10 (both B 2u ), ν 11 ν 12 (both B 3u ). Given this, how many fundamentals are Raman active? How many are IR active? Which modes, if any, are degenerate? Answer these questions before lab. Raman spectra of tetrahedral oxoanions (XO 4 n- ) may be observed by using solid salt samples or by using aqueous solutions. Since solid samples also contain cations that may perturb the symmetry and the vibrational frequencies of polyatomic anions, solution samples are preferred for this beginning study. Aqueous solutions are more difficult to measure, however, because solubility limits the ion concentration to only a few percent of that in a pure substance, and because the solvent may cause a broad Raman scattering background. Fortunately, water exhibits only weak Raman scattering, and the symmetric stretching vibration of an oxoanion, labeled as ν 1 (A 1 ), is usually observable as the most intense and most polarized band in its Raman spectrum. Since the frequency of the ν 1 mode does not depend on the mass of the center atom, ν 1 alone determines the stretching force constant for the molecule, which is related to the strength of the X-O bond. It is much more difficult to determine these bond strengths using IR spectroscopy because ν 1 is IR inactive and water absorbs strongly in the IR region.
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Spectroscopy of ¹⁶³,¹⁶⁵Os and ¹⁶⁴Ir

Spectroscopy of ¹⁶³,¹⁶⁵Os and ¹⁶⁴Ir

Energy MeV Figure 6.2: A dssd energy spectrum showing a mother decay events occurring within 0.5 ms of recoil implantation, b mother decay events occurring within 350 µs of implantation [r]

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