Transmission Spectroscopy Technique Research Articles

The GAPS Programme at TNG

Context. HAT-P-67 b is one of the lowest-density gas giants known to date, making it an excellent target for atmospheric characterisation through the transmission spectroscopy technique. Aims. In the framework of the GAPS large programme, we collected four transit events of HAT-P-67 b with the aim of studying the exoplanet atmosphere and deriving the orbital projected obliquity. Methods. We exploited the high-precision GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio Nazionale Galileo (TNG) along with additional archival TESS photometry to explore the activity level of the host star. We performed transmission spec-troscopy, both in the visible (VIS) and in the near-infrared (NIR) wavelength range, and we analysed the Rossiter–McLaughlin (RML) effect when fitting both the radial velocities and the Doppler shadow. Based on the TESS photometry, we redetermined the transit parameters of HAT-P-67 b. Results. By modelling the RML effect, we derived a sky-projected obliquity of (2.2 ± 0.4)°, indicating an aligned planetary orbit. The chromospheric activity index log R′HK, the CCF profile, and the variability in the transmission spectrum of the Hα line suggest that the host star shows signatures of stellar activity and/or pulsation. We found no evidence of atomic or molecular species in the optical transmission spectra, with the exception of pseudo-signals corresponding to Cr I, Fe I, Ha, Na I, and Ti I. In the NIR range, we found an absorption signal of the He I triplet of 5.56−0.30+0.29% (19.0σ), corresponding to an effective planetary radius of ~3 Rp (where Rp ~ 2 RJ), which extends beyond the planet’s Roche lobe radius. Conclusions. Owing to the stellar variability and the high uncertainty of the model, we could not confirm the planetary origin of the signals found in the optical transmission spectrum. On the other hand, we were able to confirm previous detections of the infrared He I triplet, providing a 19.0σ detection. Our finding indicates that the planet’s atmosphere is evaporating.

Transmission spectroscopy analyses of Jovian planets with Hubble Space Telescope

Studying the chemical compositions of exoplanetary atmospheres provides valuable information about the conditions and characteristics of those atmospheres, which could help search for signs of extraterrestrial life. To date, over 3,000 exoplanets have been discovered using the transit method. The transmission spectroscopy technique, which studies exoplanetary atmospheres during their transits, is widely used to study the atmosphere of transiting exoplanets. Wide Field Camera 3 (WFC3), an instrument on the Hubble Space Telescope (HST), use the transmission spectroscopy technique by observing the spectrum of light curves of transiting exoplanets in optical and infrared wavelengths, which could reveal some molecular absorption in the exoplanetary atmosphere. In this work, we study the atmospheres of 20 transiting exoplanets that are Jovian planets. Light curves of these exoplanets observed by the WFC3 are used to analyze their physical properties using the Iraclis package and transit depth using the TransitFit package, a python exoplanetary fitting package based on nested sampling algorithms. Our physical parameters from TransitFit are approximately the same as those in previous literature. Finally, TauREx 3, a fully Bayesian spectral retrieval code, analyzes the transit depth per wavelength channel and reveals atmospheric compositions of these exoplanetary atmospheres. One notable finding from our analysis is the detection of 5−3+8% H2O abundance in the atmosphere of WASP-63 b.

No Detection of Sodium in the Atmosphere of the Warm Neptune HD 106315c

We analyzed archival data of the warm Neptune HD 106315c, an exoplanet with an extended atmosphere orbiting an F-type star with a 21 days period. We used data from the HARPS instrument covering three transits and employed the high-resolution transmission spectroscopy technique. Our analysis yielded a non-detection of sodium with an upper limit of 0.24% on the depth of the planetary feature. This can hint at the presence of Rayleigh scattering in the atmosphere and/or clouds in the upper atmosphere. The HD 106315 system with its two Neptune-sized planets remains an intriguing target for comparative planetology in the starting era of JWST and the upcoming Ariel mission.

WASP-127b: a misaligned planet with a partly cloudy atmosphere and tenuous sodium signature seen by ESPRESSO

Context.The study of exoplanet atmospheres is essential for understanding the formation, evolution, and composition of exoplanets. The transmission spectroscopy technique is playing a significant role in this domain. In particular, the combination of state-of-the-art spectrographs at low- and high-spectral resolution is key to our understanding of atmospheric structure and composition.Aims.We observed two transits of the close-in sub-Saturn-mass planet, WASP-127b, with ESPRESSO in the frame of the Guaranteed Time Observations Consortium. We aim to use these transit observations to study the system architecture and the exoplanet atmosphere simultaneously.Methods.We used the Reloaded Rossiter-McLaughlin technique to measure the projected obliquityλand the projected rotational velocityveq⋅sin(i*). We extracted the high-resolution transmission spectrum of the planet to study atomic lines. We also proposed a new cross-correlation framework to search for molecular species and we applied it to water vapor.Results.The planet is orbiting its slowly rotating host star (veq⋅sin(i*) = 0.53−0.05+0.07km s−1) on a retrograde misaligned orbit (λ= −128.41−5.46+5.60°). We detected the sodium line core at the 9-σconfidence level with an excess absorption of 0.34 ± 0.04%, a blueshift of 2.74 ± 0.79 km s−1, and a full width at half maximum of 15.18 ± 1.75 km s−1. However, we did not detect the presence of other atomic species but set upper limits of only a few scale heights. Finally, we put a 3-σupper limit on the average depth of the 1600 strongest water lines at equilibrium temperature in the visible band of 38 ppm. This constrains the cloud-deck pressure between 0.3 and 0.5 mbar by combining our data with low-resolution data in the near-infrared and models computed for this planet.Conclusions.WASP-127b, with an age of about 10 Gyr, is an unexpected exoplanet by its orbital architecture but also by the small extension of its sodium atmosphere (~7 scale heights). ESPRESSO allows us to take a step forward in the detection of weak signals, thus bringing strong constraints on the presence of clouds in exoplanet atmospheres. The framework proposed in this work can be applied to search for molecular species and study cloud-decks in other exoplanets.

Shape control of plasmonic gold nanoparticles and its application to vacuum-free bulk hetero-junction solar cells

The plasmonic gold (Au) nanoparticles (NPs) with different shapes were synthesized and characterized. The Au nanospheres (NSPs) had a size of ~ 7 nm, while the Au nanorods (NRs) had a size of ~ 7 nm of width and ~ 23 nm of length, which were measured from electron transmission spectroscopy (TEM) technique. The Au NPs with different shapes were incorporated into the hole transport layer (HTL) of solar cell device, which led to improving light absorption and scattering of photoactive layer, eventually leading to the increase of device performance. The surface morphology of device’s active layer was optimized by deposition of 20 nm thin ZnO buffer layer between the active layer and the electrode. Finally, the device with the structure of glass/indium tin oxide (ITO)/(polyethylene dioxy thiophene doped with polystyrene-sulfonic acid (PEDOT:PSS) + Au NRs)/active layer/zinc oxide (ZnO)/E-GaIn showed a power conversion efficiency (PCE) of ~ 6%.

Synthesis and Characterization of Cu-Doped SnO<sub>2</sub> Thin Films by Aerosol Pyrolysis Technique for Gas Sensor Application

Thin films of un-doped and Cu-doped tin oxide were synthesized on quartz substrates by the purpose-built aerosol pyrolysis apparatus from 0.2 M SnCl4.5H2O – ethanol solution. CuCl2.2H2O was used as a source of Cu dopant. The Cu dopant of 1, 3 and 5 wt.% were used for doping SnO2 film. The morphological, structural, optical and electrical properties under the influence of the Cu-doping was examined by FE-SEM, XRD, UV-Vis transmission spectroscopy and Hall effect measurement technique. XRD patterns of all films exhibited rutile-phase SnO2. The doping content of 1%Cu improved the film crystallinity. The Cu doping content decreased optical bandgap from 4.36 eV for undoped SnO2 to 4.28 eV for 3%Cu-doped SnO2. The further Cu doping content increased the bandgap energy to 4.32 eV. The resistivity was increased for doping of Cu 1% but it was decreased with further increasing in Cu-doping contents

An Observational Diagnostic for Distinguishing between Clouds and Haze in Hot Exoplanet Atmospheres

Abstract The nature of aerosols in hot exoplanet atmospheres is one of the primary vexing questions facing the exoplanet field. The complex chemistry, multiple formation pathways, and lack of easily identifiable spectral features associated with aerosols make it especially challenging to constrain their key properties. We propose a transmission spectroscopy technique to identify the primary aerosol formation mechanism for the most highly irradiated hot Jupiters (HIHJs). The technique is based on the expectation that the two key types of aerosols—photochemically generated hazes and equilibrium condensate clouds—are expected to form and persist in different regions of a highly irradiated planet’s atmosphere. Haze can only be produced on the permanent daysides of tidally locked hot Jupiters, and will be carried downwind by atmospheric dynamics to the evening terminator (seen as the trailing limb during transit). Clouds can only form in cooler regions on the nightside and morning terminator of HIHJs (seen as the leading limb during transit). Because opposite limbs are expected to be impacted by different types of aerosols, ingress and egress spectra, which primarily probe opposing sides of the planet, will reveal the dominant aerosol formation mechanism. We show that the benchmark HIHJ, WASP-121b, has a transmission spectrum consistent with partial aerosol coverage and that ingress–egress spectroscopy would constrain the location and formation mechanism of those aerosols. In general, using this diagnostic we find that observations with the James Webb Space Telescope and potentially with the Hubble Space Telescope should be able to distinguish between clouds and haze for currently known HIHJs.

Transmission spectrum of Venus as a transiting exoplanet

On 5-6 June 2012, Venus will be transiting the Sun for the last time before 2117. This event is an unique opportunity to assess the feasibility of the atmospheric characterisation of Earth-size exoplanets near the habitable zone with the transmission spectroscopy technique and provide an invaluable proxy for the atmosphere of such a planet. In this letter, we provide a theoretical transmission spectrum of the atmosphere of Venus that could be tested with spectroscopic observations during the 2012 transit. This is done using radiative transfer across Venus' atmosphere, with inputs from in-situ missions such as Venus Express and theoretical models. The transmission spectrum covers a range of 0.1-5 {\mu}m and probes the limb between 70 and 150 km in altitude. It is dominated in UV by carbon dioxide absorption producing a broad transit signal of ~20 ppm as seen from Earth, and from 0.2 to 2.7 {\mu}m by Mie extinction (~5 ppm at 0.8 {\mu}m) caused by droplets of sulfuric acid composing an upper haze layer above the main deck of clouds. These features are not expected for a terrestrial exoplanet and could help discriminating an Earth-like habitable world from a cytherean planet.

Ultrafast Dynamics and Nonlinear Optical Responses from sp2- and sp3-Hybridized Domains in Graphene Oxide

The ultrafast relaxation dynamics and nonlinear optical response in single- and few-layered graphene oxide (GO) were studied by ultrafast optical differential transmission spectroscopy and Z-scan technique using various pump intensities. It was found that charge carriers with subpicosecond-to-picosecond dynamics from sp2-hybridized domains dominate the ultrafast response at low pump intensities, like graphene. Surprisingly, the influence of two-photon absorption from sp3-hybridized domains on the transient absorption signal becomes increasingly strong with pump intensities. On the basis of heterogeneous ultrafast dynamics of GO with saturable absorption in sp2 domains and two-photon absorption in sp3 domains, the nonlinear optical response can be tailored by manipulation of the degree and location of oxidation on GO sheets; this unravels the important role of sp3 domains in graphene optics and will facilitate the potential applications of GO in optoelectronics.

Detecting the quality of glycerol monolaurate: A method for using Fourier transform infrared spectroscopy with wavelet transform and modified uninformative variable elimination

Glycerol monolaurate (GML) products contain many impurities, such as lauric acid and glucerol. The GML content is an important quality indicator for GML production. A hybrid variable selection algorithm, which is a combination of wavelet transform (WT) technology and modified uninformative variable eliminate (MUVE) method, was proposed to extract useful information from Fourier transform infrared (FT-IR) transmission spectroscopy for the determination of GML content. FT-IR spectra data were compressed by WT first; the irrelevant variables in the compressed wavelet coefficients were eliminated by MUVE. In the MUVE process, simulated annealing (SA) algorithm was employed to search the optimal cutoff threshold. After the WT-MUVE process, variables for the calibration model were reduced from 7366 to 163. Finally, the retained variables were employed as inputs of partial least squares (PLS) model to build the calibration model. For the prediction set, the correlation coefficient ( r) of 0.9910 and root mean square error of prediction (RMSEP) of 4.8617 were obtained. The prediction result was better than the PLS model with full-spectra data. It was indicated that proposed WT-MUVE method could not only make the prediction more accurate, but also make the calibration model more parsimonious. Furthermore, the reconstructed spectra represented the projection of the selected wavelet coefficients into the original domain, affording the chemical interpretation of the predicted results. It is concluded that the FT-IR transmission spectroscopy technique with the proposed method is promising for the fast detection of GML content.

Optical properties of the new potential infrared-detectors Cu(I) 2SO 3 · M(II)SO 3 · 2H 2O (M = Cu, Fe, Mn, and Cd) series and the influence of M(II) exchange

The optical absorption of mixed-valence sulfites such as Cu(I) 2SO 3 · M(II)SO 3 · 2H 2O [M = Cu, Fe, Mn, or Cd] were studied and the influence of the M(II) cation on this parameter. A transmission spectroscopy technique was used to measure the optical band gap energies ( E g) in the infrared region and the E g of Cu(I) 2SO 3 · Cu(II)SO 3 · 2H 2O was estimated using a numerical fitting method that can be described empirically by E g ( χ P ) = - 0.62 χ P 2 + 1.88 χ P - 0.5 , where χ P is Pauling’s electronegativity of metal M. The obtained values were in the interval 0.85–0.95 eV, representing a narrow E g, which can identify these compounds as potential infrared-detectors.

Density dependence of the spectral dielectric function across a Fano resonance

We study the effects of photocarrier density on a magnetically induced Fano resonance in GaAs, using a combined phase-amplitude transmission spectroscopy technique. By comparing our results to an extension of the Fano model we measure the relative contributions of two, usually undistinguished, effects of the photocarriers: the screening of the inter-Landau-level Coulomb coupling, and the induced collisional broadening of the coupled discrete-state/continuum natural linewidth.

Comparison of IR Techniques for the Characterization of Construction Cement Minerals and Hydrated Products

The influence of FT-IR sampling techniques on the characterization of cement systems was investigated. Three FT-IR techniques were used to study tricalcium silicate (C3S), hydrated C3S, calcium hydroxide, and calcium silicate hydrate (C–S–H). They include transmission spectroscopy (TS), photoacoustic spectroscopy (PAS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The TS technique (using KBr pellets) was the most labor-intensive but was found to give the simplest spectra with well-defined bands. The PAS technique was found to be the simplest technique but yielded bands at lower wavenumber than TS. DRIFTS was determined to be a good alternative for cement powders since it provided spectra similar to those for the TS technique. DRIFTS required more sample preparation than PAS but less sample preparation than the KBr pellet technique.

Pulsed photoacoustic detection technique applied to the study of multiphoton absorption in molecules

A pulsed laser photoacoustic technique is described. It is optimized for the simultaneous investigations of multiphoton absorption processes as well as rotational relaxation and vibration relaxation studies. The experimental procedure is presented, concerning the calibration of the photoacoustic detector/cell set-up, applying the transmission spectroscopy technique. The obtained relationships, which can be alternatively used for the sensitivity curve S(p, gamma , T) of the apparatus, are analysed. A previously proposed model is confirmed.

Photoacoustic study of collisional effects on rotational relaxation processes induced by infrared multiphoton absorption

The novel experimental approach is applied to investigate the cross sections for rotational relaxation σ rot.-rel. in the SF 6 -Ar mixtures irradiated by pulsed CO 2 laser line. The applied method is the pulsed photoacoustic technique, and it is based on proposal for σ rot.-rel. determination by transmission spectroscopy technique. The collisional effects have been investigated for the 0.1-0.8 J/cm 2 laser fluence range. Also, the collisional effects on rotational and translational temperature (T R ) for SF 6 -Ar mixtures have been calculated