Near-infrared Transmission Spectra Research Articles

Stability and Detectability of Exomoons Orbiting HIP 41378 f, a Temperate Jovian Planet with an Anomalously Low Apparent Density

Moons orbiting exoplanets (“exomoons”) may hold clues about planet formation, migration, and habitability. In this work, we investigate the plausibility of exomoons orbiting the temperate (T eq = 294 K) giant (R = 9.2 R ⊕) planet HIP 41378 f, which has been shown to have a low apparent bulk density of 0.09 g cm−3 and a flat near-infrared transmission spectrum, hinting that it may possess circumplanetary rings. Given this planet’s long orbital period (P ≈ 1.5 yr), it has been suggested that it may also host a large exomoon. Here, we analyze the orbital stability of a hypothetical exomoon with a satellite-to-planet mass ratio of 0.0123 orbiting HIP 41378 f. Combining a new software package, astroQTpy, with REBOUND and EqTide, we conduct a series of N-body and tidal migration simulations, demonstrating that satellites up to this size are largely stable against dynamical escape and collisions. We simulate the expected transit signal from this hypothetical exomoon and show that current transit observations likely cannot constrain the presence of exomoons orbiting HIP 41378 f, though future observations may be capable of detecting exomoons in other systems. Finally, we model the combined transmission spectrum of HIP 41378 f and a hypothetical moon with a low-metallicity atmosphere and show that the total effective spectrum would be contaminated at the ∼10 ppm level. Our work not only demonstrates the feasibility of exomoons orbiting HIP 41378 f but also shows that large exomoons may be a source of uncertainty in future high-precision measurements of exoplanet systems.

Detection of apple moldy cores using transmittance spectroscopy combined with supervised classifier comparison and parameter optimization

It is difficult to determine which apples have moldy cores just by looking at the outside of the apple. In the present study, we investigated identifying moldy cores using near-infrared transmittance spectra. First, input spectral features selected by noise adjusted principal component analysis (NAPCA) for back propagation artificial neural network (BP ANN) was used to reduce the dimensions of the original data. Then, four factors and five levels uniform design of the input nodes, training functions, transfer layer functions and output layer functions for NAPCA-BP ANN optimization is proposed. And the original data were input into NAPCA-BP ANN to obtain the recognition accuracy and NAPCA-support vector machine (SVM) was as a comparative recognition model. The results showed that through the uniform design-based NAPCA-BP ANN optimization, the NAPCA method had higher identification accuracy, precision, recall and F1 score, than either full spectrum or principal component analysis. Being assessed by different ratio of model test, functions in the hidden layer and output layer of NAPCA-BP ANN, the proposed method achieved the best accuracy to 98.03%. The accuracy, precision, recall and F1 score based on NAPCA-BP ANN were 3.92%, 2.86%, 2.78% and 2.82% higher than those based on NAPCA-SVM, respectively. This method provides a theoretical basis for the development of on-line monitoring of the internal quality of apples.

A Rapid and Accurate Quantitative Analysis of Cellulose in the Rice Bran Layer Based on Near-Infrared Spectroscopy.

Cultivating rice varieties with lower cellulose content in the bran layer has the potential to enhance both the nutritional value and texture of brown rice. This study aims to establish a rapid and accurate method to quantify cellulose content in the bran layer utilizing near-infrared spectroscopy (NIRS), thereby providing a technical foundation for the selection, screening, and breeding of rice germplasm cultivars characterized by a low cellulose content in the bran layer. To ensure the accuracy of the NIR spectroscopic analysis, the potassium dichromate oxidation (PDO) method was improved and then used as a reference method. Using 141 samples of rice bran layer (rice bran without germ), near-infrared diffuse reflectance (NIRdr) spectra, near-infrared diffuse transmittance (NIRdt) spectra, and fusion spectra of NIRdr and NIRdt were used to establish cellulose quantitative analysis models, followed by a comparative evaluation of these models' predictive performance. Results indicate that the optimized PDO method demonstrates superior precision compared to the original PDO method. Upon examining the established models, their predictive capabilities were ranked in the following order: the fusion model outperforms the NIRdt model, which in turn surpasses the NIRdr model. Of all the fusion models developed, the model exhibiting the highest predictive accuracy utilized fusion spectra (NIRdr-NIRdt (1st der)) derived from preprocessed (first derivative) diffuse reflectance and transmittance spectra. This model achieved an external predictive R2p of 0.903 and an RMSEP of 0.213%. Using this specific model, the rice mutant O2 was successfully identified, which displayed a cellulose content in the bran layer of 3.28%, representing a 0.86% decrease compared to the wild type (W7). The utilization of NIRS enables quantitative analysis of the cellulose content within the rice bran layer, thereby providing essential technical support for the selection of rice varieties characterized by lower cellulose content in the bran layer.

Si/Organic Integrated Narrowband Near-Infrared Photodetector.

Spectrally selective narrowband photodetection is critical for near-infrared (NIR) imaging applications, such as for communicationand night-vision utilities. It is a long-standing challenge for detectors based on silicon, to achieve narrowband photodetection without integrating any optical filters. Here, this work demonstrates a NIR nanograting Si/organic (PBDBT-DTBT:BTP-4F) heterojunction photodetector (PD), which for the first time obtains the full-width-at-half-maximum (FWHM) of only 26nm and fast response of 74 µs at 895nm. The response peak can be successfully tailored from 895 to 977nm. The sharp and narrow response NIR peak is inherently attributed to the coherent overlapping between the NIR transmission spectrum of organic layer and diffraction enhanced absorption peak of patterned nanograting Si substrates. The finite difference time domain (FDTD) physics calculation confirms the resonant enhancement peaks, which is well consistent with the experiment results. Meanwhile, the relative characterization indicates that the introduction of the organic film can promote carrier transfer and charge collection, facilitating efficient photocurrent generation. This new device design strategy opens up a new window in developing low-cost sensitive NIR narrowband detection.

Featureless transmission spectra of 12 giant exoplanets observed by GTC/OSIRIS

Context. Exoplanet atmospheres are the key to understanding the nature of exoplanets. To this end, transit spectrophotometry provides us opportunities to investigate the physical properties and chemical compositions of exoplanet atmospheres. Aims. We aim to detect potential atmospheric signatures in 12 gaseous giant exoplanets using transit spectrophotometry and we try to constrain their atmospheric properties. Methods. The targets of interest were observed using transit spectrophotometry with the GTC OSIRIS instrument. We estimated the transit parameters and obtained the optical transmission spectra of the target planets using a Bayesian framework. We analyzed the spectral features in the transmission spectra based on atmospheric retrievals. Results. Most of the observed transmission spectra were found to be featureless, with only the spectrum of CoRoT-1b showing strong evidence for atmospheric features. However, in combination with the previously published near-infrared transmission spectrum, we found multiple interpretations for the atmosphere of CoRoT-1b due to the lack of decisive evidence for alkali metals or optical absorbers. Conclusions. Featureless spectra are not necessarily indicative of cloudy atmospheres if they poorly constrain the altitudes of cloud decks. Precise constraints on the models of hazes and clouds strongly depend on the significance of the observed spectral features. Further investigations on these exoplanets, especially CoRoT-1b, are required to confirm the properties of their atmospheres.

Continuous Ultra‐Broadband Near‐Infrared Sc2O3‐Based Nanophosphor Realized by Spectral Bridge of Cr3+‐Yb3+‐Cr4+ for Multiple Optical Applications

AbstractCr3+‐activated near‐infrared (NIR) phosphors are one of the most influential candidates for the new generation of intelligent NIR phosphor‐converted light‐emitting diode (pc‐LED) light sources. For spectral analysis, the broader the spectrum, the more useful information it contains. Herein, ultra‐broadband Cr‐activated Sc2O3 nanophosphors, which exhibit NIR ultra‐broadband from 650 to 1600 nm, are developed by the sol–gel method. This ultra‐broadband emission originates from the presence of Cr3+ and Cr4+, two luminescent centers confirmed by diffuse reflection spectra, electron paramagnetic resonance, time‐resolved photoluminescence spectra, and temperature‐dependent emission spectra. The nanophosphor exhibits excellent temperature‐sensing performance with SA = 4.102% K−1 and SR = 1.855% K−1. Co‐doping Yb3+ into Sc2O3 nanophosphors builds the Cr3+‐Yb3+‐Cr4+ model to bridge the spectral gap located at 1000 nm, forming a continuous NIR ultra‐broadband spectrum ranging from 650 to 1600 nm for the first time. Moreover, the introduction of Yb3+ improves the thermal stability of nanophosphors from 29.49% to 50.65% at 150 °C. The NIR transmission spectra of water, ethanol, and peanut oil demonstrate that Sc2O3:Cr3+‐Yb3+‐Cr4+ NIR nanophosphors favor potential applications in spectral analysis. The construction of a Cr3+‐Yb3+‐Cr4+ spectral bridge for realizing NIR ultra‐broadband phosphors based on cheap blue LEDs provides novel and effective insights.

Structure and Optical Properties of Transparent Cobalt-Doped ZnO Thin Layers

Transparent thin layers of cobalt-doped ZnO were produced with the pulsed laser deposition method. The cobalt content of the original solid solution was 20% at. The crystallographic structure was examined by X-ray diffraction, which showed that the fabricated layers crystallized in the wurtzite phase and had a dominant orientation along the a-axis. The texture coefficient (increasing from F = 0.08 for the non-annealed layer to F = 0.94 for the annealed layer at 400 °C) and grain size (D = 110 ÷ 140 nm) were calculated. Optical constants, such as the refractive index n (1.62) and the extinction coefficient k (0.1 ÷ 0.4), were determined from the ultraviolet–visible–near-infrared transmission spectrum using the envelope method. The value of the optical band gap was determined, which is lower than for pure ZnO. Increasing the annealing temperature of the ZnO:Co layer increases the Urbach energy from 0.20 to 0.25 eV, which shows the difference in the type of growth defects in the ZnO matrix.

BP neural network to predict shelf life of channel catfish fillets based on near infrared transmittance (NIT) spectroscopy

The objective of this research was to establish shelf-life prediction model of channel catfish fillets by Back-propagation (BP) neural network technology based on near infrared transmittance (NIT). First, freshness prediction model of channel catfish fillets was established based on the chemical analysis data (total volatile basic nitrogen (TVB-N), K value, thiobarbituric acid reactive substance (TBARS) and trimethylamine (TMA)) and NIT spectra (850–1050 nm). The linear correlation coefficient (R2: 0.667–0.887) showed a good performance of the freshness model prediction. Then, BP neural network was applied to establish the shelf-life prediction model of catfish fillets under temperature fluctuation (−6 to −18 °C). The end effective accumulated temperature of frozen catfish fillets was 10,278.4 h °C. The prediction model showed a great stability (above 93 %) and accuracy (above 90 %) as the structure of BP neural network was 4–7–1. Therefore, this study provided a practical basis and technical supports for the establishment of shelf-life prediction model of freshwater fillets by BP neural network based on NIT spectroscopy.

A discrimination model for dead cocoons using near-infrared transmission spectra analyses

Silk from cocoons is widely used as a functional raw material for alleviating skin diseases, improving memory, preventing diabetes, and as antioxidants. Dead cocoons are screened to utilize silk, resulting in poor marketability and cross-contamination of other cocoons. Considering that the screening of cocoons is performed manually to date, there is a high demand for automating this process. Spectroscopic analyses are actively used for non-destructive analysis methods. In this study, a discrimination model was developed to determine whether a cocoon is dead or alive using the near-infrared transmission spectra. A total of 367 normal cocoons and 152 dead cocoons were used in our experiment, and the cocoons were cut to determine whether they were dead or alive. The near-infrared transmission spectra were obtained for each cocoon for the wavelength band 900–1700 nm. Nine pre-processing methods were applied to eliminate spectral noise; pre-processing related to normalization demonstrated significant difference compared to other pre-processing methods. Furthermore, principal component analysis (PCA) was used to visualize the distribution of spectra, and discrimination models were developed using the wavelength range of the highest transmittance intensity and partial least squares-discriminant analysis (PLS-DA). PCA successfully discriminated between normal and dead cocoons. The discrimination model according to the wavelength range of the highest transmittance intensity demonstrated a discriminant accuracy of 94.80 %. Using PLS-DA with range normalization pre-processing spectra, the discriminant accuracies were 94.56 % and 94.64 % for calibration and validation, respectively. Thus, the proposed method can help discriminate between normal and dead cocoons non-destructively using the near infrared transmission spectra. • A discrimination model is developed to discriminate live and dead cocoons. • The model is based on near-infrared transmission spectra. • Transmission spectra at 904–1707 nm were acquired and analyzed. • A discriminant accuracy of 94.80 % was demonstrated by the model. • This method can help discriminate between dead and live cocoons non-destructively.

Improved performance of PCBM/MAPbI3 heterojunction photovoltaic cells with the treatment of a saturated BCP/IPA solution

The interfacial contact quality between the hydrophilic MAPbI 3 and hydrophobic PCBM thin films are improved by using the treatment of a saturated bathocuproine/isopropanol (BCP/IPA) solution, which largely increases the power conversion efficiency (PCE) from 12.96% to 18.67%. The atomic force microscopic images, water-droplet contact angle images, viscosity measurement results and near-infrared transmittance spectra show that the increased open-circuit voltage (V OC ) is related to the formation of a denser PCBM thin film and the better contact quality of the PCBM/MAPbI 3 heterojunction. Besides, the power-dependent current density-voltage (J-V) curves show that the lower defect density in the solar cells results in the higher V OC . In other words, the treatment of a saturated BCP/IPA solution can decrease the defect density of the PCBM/MAPbI 3 heterojunction and thereby boosting the photovoltaic performance and extending the device lifespan. • The saturated BCP/IPA solution treatment increases the density of the PCBM thin film. • The saturated BCP/IPA solution treatment strengthens the contact quality at PCBM/MAPbI 3 interface. • The saturated BCP/IPA solution treatment increases the hydrophobicity of PCBM/MAPbI 3 heterojunction. • The saturated BCP/IPA solution treatment improves the PCE of photovoltaic cells from 12.69% to 18.67%.

Evaluation of optical properties of tofu samples produced with different coagulation temperatures and times using near-infrared transmission spectroscopy

To investigate the feasibility of using near-infrared (NIR) spectroscopy to evaluate the coagulation extent of tofu, the optical properties of tofu samples obtained with different coagulation temperatures and times were measured in the wavelength range 1300–1800 nm. The apparent absorbance was measured using the NIR transmission spectrum, and then divided into absorption and scattering components by curve fitting. The apparent absorbance increased over the entire wavelength range as the coagulation temperature increased, in which the scattering increase was dominant over that of the absorption. The viscosity was measured as an index of the physical properties of tofu, which increased with the coagulation temperature and had a high correlation (R2 = 0.803) with one of the fitting parameters of the scattering. The microstructure of the tofu became finer as the coagulation temperature increased, which suggests that the increase in scattering might be due to changes in the microstructure. Furthermore, the light scattering increased with the coagulation time as well as with the coagulation temperature. The increase in scattering with the coagulation time followed the first-order reaction kinetics. Both scattering intensity and increase speed were larger at shorter wavelengths. This can be explained by the theory of Mie scattering and multiple scattering, indicating that scattering measurements at shorter wavelengths are useful for monitoring of coagulation. Thus, light scattering measurements using NIR spectroscopy are promising for investigating the physical properties of tofu.

The First Near-infrared Transmission Spectrum of HIP 41378 f, A Low-mass Temperate Jovian World in a Multiplanet System

Abstract We present a near-infrared transmission spectrum of the long-period (P = 542 days), temperate (T eq = 294 K) giant planet HIP 41378 f obtained with the Wide-Field Camera 3 instrument aboard the Hubble Space Telescope (HST). With a measured mass of 12 ± 3 M ⊕ and a radius of 9.2 ± 0.1 R ⊕, HIP 41378 f has an extremely low bulk density (0.09 ± 0.02 g cm−3). We measure the transit depth with a median precision of 84 ppm in 30 spectrophotometric channels with uniformly sized widths of 0.018 μm. Within this level of precision, the spectrum shows no evidence of absorption from gaseous molecular features between 1.1 and 1.7 μm. Comparing the observed transmission spectrum to a suite of 1D radiative-convective-thermochemical-equilibrium forward models, we rule out clear, low-metallicity atmospheres and find that the data prefer high-metallicity atmospheres or models with an additional opacity source, such as high-altitude hazes and/or circumplanetary rings. We explore the ringed scenario for HIP 41378 f further by jointly fitting the K2 and HST light curves to constrain the properties of putative rings. We also assess the possibility of distinguishing between hazy, ringed, and high-metallicity scenarios at longer wavelengths with the James Webb Space Telescope. HIP 41378 f provides a rare opportunity to probe the atmospheric composition of a cool giant planet spanning the gap in temperature, orbital separation, and stellar irradiation between the solar system giants, directly imaged planets, and the highly irradiated hot Jupiters traditionally studied via transit spectroscopy.

The First Near-infrared Transmission Spectrum of HIP 41378 f, A Low-mass Temperate Jovian World in a Multiplanet System

The First Near-infrared Transmission Spectrum of HIP 41378 f, A Low-mass Temperate Jovian World in a Multiplanet System

Data fusion of near-infrared diffuse reflectance spectra and transmittance spectra for the accurate determination of rice flour constituents

The data fusion method effectively fuses multiple complementary inputs for highly accurate analysis. The spectral signals collected by near-infrared diffuse reflectance (NIRr) and diffuse transmission (NIRt) contain various information on the physical structure and chemical composition of the sample. Thus, the data fusion method (for NIRr and NIRt) can be used to further improve the accuracy of the NIR quantitative analysis method. The NIR spectroscopic analysis of protein content (PC), amylose content (AC), and fat content (FC) of rice can be used to select high-quality rice varieties. The data obtained using the NIR spectroscopic analysis method for rice flour were used to optimize NIRr and NIRt data fusion and verify the feasibility of this method to achieve more accurate quantitative analysis. Two types of rice flour spectra, NIRr spectra and NIRt spectra, were processed by different pretreatment methods to obtain high-quality fused spectra. The combinations of different pretreatment methods and spectral ranges were subsequently used for the optimization and calibration of partial least square models. The results reveal that the models of the fused spectra processed by the first derivative [NIRr–NIRt (1 der)] exhibit optimal prediction accuracy. The root mean square errors of prediction (RMSEPs) of the optimal NIRr–NIRt (1 der) PC, AC, and FC models were 0.280, 1.240, and 0.165, respectively, which were lower than those of the NIRr and NIRt models. The results show that the fusion of NIRr and NIRt data can achieve accurate detection of rice flour constituents, indicating the method has potential for further development and application.

Solar‐NIRT: Identification of PV‐module backsheets in the field with natural sunlight

AbstractReliable and durable solar power plants require PV modules with high‐grade polymer encapsulants and backsheets (BSs). For performance analyses of PV installations fast, reliable and non‐destructive methods for determining composition and degradation state of polymer components need to be developed. Here, we show that the structure of some common polymer BSs can be determined in the field in real time by analyzing near‐infrared transmission (NIRT) spectra collected under illumination with natural sunlight. The potential of this “Solar‐NIRT” method was probed by field measurements on a multi‐MW PV power plant where four major BS types were identified by multispectral cross‐sectional Raman imaging. Additionally, degradation of a particular BS type was found to result in distinct changes in NIRT spectra allowing the degraded BSs to be classified as a separate type. Principal component analysis (PCA) applied to a collection of 62 Solar‐NIRT spectra allowed to create a map of five clusters, each corresponding to a particular BS type. The feasibility of using the PCA cluster map for the identification of unknown samples was shown on a test set of 13 different BSs. The Solar‐NIRT is relatively fast, non‐invasive, selective, can be upgraded to a non‐contact regime making it a promising tool for high‐throughput characterization.

Investigation of deep levels in semi-insulating vanadium-doped 4H-SiC by photocurrent spectroscopy

We measured spectral-resolved photocurrent in a wide range of photon energies from 0.68 eV to 4.10 eV, current-voltage characteristics, and mid to near-infrared transmittance spectra on a semi-insulating 4H-SiC wafer at room temperature. We identified four deep levels, their energies, and localization radii. The model considers the defects' wavefunction as a linear combination of s- and p-states. Such a linear combination leads to the mixture of dipole allowed and forbidden transitions. The forbidden transitions contribute to a broad photocurrent spectrum, and the allowed transitions appear as sharp photocurrent peaks. The width of photocurrent peaks is related to the localization radius of deep levels.

Indications for very high metallicity and absence of methane in the eccentric exo-Saturn WASP-117b

Aims. We investigate the atmospheric composition of the long-period (Porb = 10 days) eccentric exo-Saturn WASP-117b. WASP-117b could be similar in atmospheric temperature and chemistry to WASP-107b. In mass and radius, WASP-117b is similar to WASP-39b, which allows a comparative study of these planets. Methods. We analyzed a near-infrared transmission spectrum of WASP-117b taken with the Hubble Space Telescope (HST) WFC3 G141, which was reduced with two independent pipelines. High-resolution measurements were taken with VLT/ESPRESSO in the optical. Results. We report the robust (3σ) detection of a water spectral feature. In a 1D atmosphere model with isothermal temperature, uniform cloud deck, and equilibrium chemistry, the Bayesian evidence of a retrieval analysis of the transmission spectrum indicates a preference for a high atmospheric metallicity [Fe/H] = 2.58−0.37+0.26 and clear skies. The data are also consistent with a lower metallicity composition [Fe/H] < 1.75 and a cloud deck between 10−2.2 and 10−5.1 bar, but with weaker Bayesian preference. We retrieve a low CH4 abundance of <10−4 volume fraction within 1σ and <2 × 10−1 volume fraction within 3σ. We cannot constrain the equilibrium temperature between theoretically imposed limits of 700 and 1000 K. Further observations are needed to confirm quenching of CH4 with Kzz ≥ 108 cm2 s−1. We report indications of Na and K in the VLT/ESPRESSO high-resolution spectrum with substantial Bayesian evidence in combination with HST data.

Convolution Neural Network Application in the Simultaneous Detection of Gender and Variety of Silkworm (Bombyx mori) Cocoons

Convolution neural network (CNN) has been widely studied in the field of computer vision with good results, and a lot of research is still needed to show its application effect in the near-infrared spectroscopy with 1-D input data and small sample set. In this paper, the near-infrared diffuse transmission spectra of 2386 silkworm (Bombyx mori) cocoons from the 4th day of cocooning to the 13th day before turning into moths were collected. After the mean center preprocessing, CNN, SVM and LDA were used to model and analyze. Experimental results showed that, with the convolution kernel width 100, the convolution kernel num 16, and the stride 50, the good generalization effect of CNN model can be achieved when the simple structure of 6 layers without pooling layer was adopted. For each day, the gender prediction accuracy of cocoons is more than 90% and the highest accuracy is 100% on the 6th day with optimal model CNN. For each day, the variety prediction accuracy of cocoons is more than 98% and the highest accuracy is 100% with optimal model LDA. There is no significant correlation between pupa age and the gender and variety detection accuracy of silkworm cocoons. This can help broaden the pupa gender identification time in the actual production of silkworm egg farms. In the application of simultaneous identification of gender and variety, CNN model has the highest accuracy of 94%, LDA model has the medium accuracy of 92.5%, and SVM model has the lowest accuracy of 89.5%.

How much anharmonicity is in vibrational spectra of CH3I and CD3I?

This work presents new experimental and theoretical insights on vibrational spectra of CH3I and CD3I in the liquid phase. For the first time, we provided the contributions from different vibrational modes to mid-infrared (MIR) and near-infrared (NIR) spectra and estimated the extent of anharmonicity in the MIR region. Direct comparison of the intensities from ATR-IR and NIR transmission spectra was possible due to normalization of ATR-IR spectra. As a reference for normalization, we applied the area of the νs(CH3)/νs(CD3) band recorded in transmission mode. Our results show that the corresponding vibrational modes of CH3I and CD3I have similar contributions to the total intensity (MIR + NIR), however, these contributions are distributed in a different way between MIR and NIR regions. As expected, most of intensity in MIR spectra originates from the fundamental transitions (>90%). The fundamental bands together with the first overtones and the binary combinations contribute to more than 99% of MIR intensity for both compounds. Therefore, reliable reconstruction of MIR spectra can be achieved by considering only these vibrational modes. On the other hand, accurate simulation of NIR spectra requires including the higher-order transitions. In the case of CD3I, the fourth-order transitions contribute to 12.7% of NIR intensity. The contributions from NIR region are significantly smaller than those from MIR range and were estimated to be 6.7% for CH3I and 2.3% for CD3I. The theoretical calculations provide a reasonable estimation of the total contribution from the fundamental bands. Yet, the calculated contributions from the anharmonic transitions are different from those obtained from the experimental data. MIR spectra of CH3I and CD3I reveal an unexpected increase in the intensity of some overtones and combination bands indicating the presence of Fermi resonances. These resonances are responsible for differences in contributions from the first overtones and binary combinations between CH3I and CD3I.

The widest broadband transmission spectrum (0.38–1.71μm) of HD 189733b from ground-based chromatic Rossiter–McLaughlin observations

Multiband photometric transit observations (spectro-photometric) have been used mostly so far to retrieve broadband transmission spectra of transiting exoplanets in order to study their atmospheres. An alternative method was proposed, and has only been used once, to recover broadband transmission spectra using chromatic Rossiter–McLaughlin observations. We use the chromatic Rossiter–McLaughlin technique on archival and new observational data obtained with the HARPS and CARMENES instruments to retrieve transmission spectra of HD 189733b. The combined results cover the widest retrieved broadband transmission spectrum of an exoplanet obtained from ground-based observation. Our retrieved spectrum in the visible wavelength range shows the signature of a hazy atmosphere, and also includes an indication for the presence of sodium and potassium. These findings all agree with previous studies. The combined visible and near-infrared transmission spectrum exhibits a strong steep slope that may have several origins, such as a super-Rayleigh slope in the atmosphere of HD 189733b, an unknown systematic instrumental offset between the visible and near-infrared, or a strong stellar activity contamination. The host star is indeed known to be very active and might easily generate spurious features in the retrieved transmission spectra. Using our CARMENES observations, we assessed this scenario and place an informative constraint on some properties of the active regions of HD 189733. We demonstrate that the presence of starspots on HD 189733 can easily explain our observed strong slope in the broadband transmission spectrum.