The Experts below are selected from a list of 49770 Experts worldwide ranked by ideXlab platform
Greg W Doppmann - One of the best experts on this subject based on the ideXlab platform.
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a Spectroscopic Technique for measuring stellar properties of pre main sequence stars
The Astronomical Journal, 2003Co-Authors: Greg W Doppmann, Daniel T JaffeAbstract:We describe a Technique for deriving effective temperatures, surface gravities, rotation velocities, and radial velocities from high-resolution near-IR spectra. The Technique matches the observed near-IR spectra to spectra synthesized from model atmospheres. Our analysis is geared toward characterizing heavily reddened pre–main-sequence stars, but the Technique also has potential applications in characterizing main-sequence and post–main-sequence stars when these lie behind thick clouds of interstellar dust. For the pre–main-sequence stars, we use the same matching process to measure the amount of excess near-IR emission (which may arise in the protostellar disks) in addition to the other stellar parameters. The information derived from high-resolution spectra comes from line shapes and the relative line strengths of closely spaced lines. The values for the stellar parameters we derive are therefore independent of those derived from low-resolution spectroscopy and photometry. The new method offers the promise of improved accuracy in placing young stellar objects on evolutionary model tracks. Tests with an artificial noisy spectrum with typical stellar parameters and a signal-to-noise ratio of 50 indicate a 1 σ error of 100 K in Teff, 2 km s-1 in v sin i, and 0.13 in continuum veiling for an input veiling of 1. If the flux ratio between the sum of the Na, Sc, and Si lines at 2.2 μm and the (2–0) 12CO band head at 2.3 μm is known to an accuracy of 10%, the errors in our best-fit value for log g will be Δ log g = 0.1–0.2. We discuss the possible systematic effects on our determination of the stellar parameters and evaluate the accuracy of the results derivable from high-resolution spectra. In the context of this evaluation, we quantitatively explore the degeneracy between temperature and gravity that has bedeviled efforts to type young stellar objects using low-resolution spectra. The analysis of high-resolution near-IR spectra of MK standards shows that the Technique yields very accurate values for the effective temperature. The greatest uncertainty in comparing our results with optical spectral typing of MK standards is in the spectral type–to–effective temperature conversion for the standards themselves. Even including this uncertainty, the 1 σ difference between the optical and infrared temperatures for dwarfs at 3000–5800 K is only 140 K. In a companion paper, we present an analysis of heavily extincted young stellar objects in the ρ Ophiuchi molecular cloud.
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a Spectroscopic Technique for measuring stellar properties of pre main sequence stars
arXiv: Astrophysics, 2003Co-Authors: Greg W Doppmann, Daniel T JaffeAbstract:We describe a Technique for deriving effective temperatures, surface gravities, rotation velocities, and radial velocities from high resolution near-IR spectra. The Technique matches the observed near-IR spectra to spectra synthesized from model atmospheres. For pre-main sequence stars, we use the same matching process to also measure the amount of excess near-IR emission. The information derived from high resolution spectra comes from line shapes and the relative line strengths of closely spaced lines. The values for the stellar parameters we derive are therefore independent of those derived from low resolution spectroscopy and photometry. The new method offers the promise of improved accuracy in placing young stellar objects on evolutionary model tracks. We discuss the possible systematic effects on our determination of the stellar parameters and evaluate the accuracy of the results derivable from high resolution spectra. The analysis of high resolution near-IR spectra of MK standards shows that the Technique gives very accurate values for the effective temperature. The biggest uncertainty in comparing our results with optical spectral typing of MK standards is in the spectral type to effective temperature conversion for the standards themselves. Even including this uncertainty, the 1 sigma difference between the optical and IR temperatures for 3000-5800 K dwarfs is only 140 K. In a companion paper (Doppmann, Jaffe, & White 2003), we present an analysis of heavily extincted young stellar objects rho Oph.
Daniel T Jaffe - One of the best experts on this subject based on the ideXlab platform.
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a Spectroscopic Technique for measuring stellar properties of pre main sequence stars
The Astronomical Journal, 2003Co-Authors: Greg W Doppmann, Daniel T JaffeAbstract:We describe a Technique for deriving effective temperatures, surface gravities, rotation velocities, and radial velocities from high-resolution near-IR spectra. The Technique matches the observed near-IR spectra to spectra synthesized from model atmospheres. Our analysis is geared toward characterizing heavily reddened pre–main-sequence stars, but the Technique also has potential applications in characterizing main-sequence and post–main-sequence stars when these lie behind thick clouds of interstellar dust. For the pre–main-sequence stars, we use the same matching process to measure the amount of excess near-IR emission (which may arise in the protostellar disks) in addition to the other stellar parameters. The information derived from high-resolution spectra comes from line shapes and the relative line strengths of closely spaced lines. The values for the stellar parameters we derive are therefore independent of those derived from low-resolution spectroscopy and photometry. The new method offers the promise of improved accuracy in placing young stellar objects on evolutionary model tracks. Tests with an artificial noisy spectrum with typical stellar parameters and a signal-to-noise ratio of 50 indicate a 1 σ error of 100 K in Teff, 2 km s-1 in v sin i, and 0.13 in continuum veiling for an input veiling of 1. If the flux ratio between the sum of the Na, Sc, and Si lines at 2.2 μm and the (2–0) 12CO band head at 2.3 μm is known to an accuracy of 10%, the errors in our best-fit value for log g will be Δ log g = 0.1–0.2. We discuss the possible systematic effects on our determination of the stellar parameters and evaluate the accuracy of the results derivable from high-resolution spectra. In the context of this evaluation, we quantitatively explore the degeneracy between temperature and gravity that has bedeviled efforts to type young stellar objects using low-resolution spectra. The analysis of high-resolution near-IR spectra of MK standards shows that the Technique yields very accurate values for the effective temperature. The greatest uncertainty in comparing our results with optical spectral typing of MK standards is in the spectral type–to–effective temperature conversion for the standards themselves. Even including this uncertainty, the 1 σ difference between the optical and infrared temperatures for dwarfs at 3000–5800 K is only 140 K. In a companion paper, we present an analysis of heavily extincted young stellar objects in the ρ Ophiuchi molecular cloud.
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a Spectroscopic Technique for measuring stellar properties of pre main sequence stars
arXiv: Astrophysics, 2003Co-Authors: Greg W Doppmann, Daniel T JaffeAbstract:We describe a Technique for deriving effective temperatures, surface gravities, rotation velocities, and radial velocities from high resolution near-IR spectra. The Technique matches the observed near-IR spectra to spectra synthesized from model atmospheres. For pre-main sequence stars, we use the same matching process to also measure the amount of excess near-IR emission. The information derived from high resolution spectra comes from line shapes and the relative line strengths of closely spaced lines. The values for the stellar parameters we derive are therefore independent of those derived from low resolution spectroscopy and photometry. The new method offers the promise of improved accuracy in placing young stellar objects on evolutionary model tracks. We discuss the possible systematic effects on our determination of the stellar parameters and evaluate the accuracy of the results derivable from high resolution spectra. The analysis of high resolution near-IR spectra of MK standards shows that the Technique gives very accurate values for the effective temperature. The biggest uncertainty in comparing our results with optical spectral typing of MK standards is in the spectral type to effective temperature conversion for the standards themselves. Even including this uncertainty, the 1 sigma difference between the optical and IR temperatures for 3000-5800 K dwarfs is only 140 K. In a companion paper (Doppmann, Jaffe, & White 2003), we present an analysis of heavily extincted young stellar objects rho Oph.
Marlan O. Scully - One of the best experts on this subject based on the ideXlab platform.
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In vivo diagnostics of early abiotic plant stress response via Raman spectroscopy.
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Narangerel Altangerel, Gombojav O. Ariunbold, Connor Gorman, Masfer Alkahtani, Eli J. Borrego, Dwight Bohlmeyer, Philip Hemmer, Michael V. Kolomiets, Joshua S. Yuan, Marlan O. ScullyAbstract:Development of a phenotyping platform capable of noninvasive biochemical sensing could offer researchers, breeders, and producers a tool for precise response detection. In particular, the ability to measure plant stress in vivo responses is becoming increasingly important. In this work, a Raman Spectroscopic Technique is developed for high-throughput stress phenotyping of plants. We show the early (within 48 h) in vivo detection of plant stress responses. Coleus (Plectranthus scutellarioides) plants were subjected to four common abiotic stress conditions individually: high soil salinity, drought, chilling exposure, and light saturation. Plants were examined poststress induction in vivo, and changes in the concentration levels of the reactive oxygen-scavenging pigments were observed by Raman microscopic and remote Spectroscopic systems. The molecular concentration changes were further validated by commonly accepted chemical extraction (destructive) methods. Raman spectroscopy also allows simultaneous interrogation of various pigments in plants. For example, we found a unique negative correlation in concentration levels of anthocyanins and carotenoids, which clearly indicates that plant stress response is fine-tuned to protect against stress-induced damages. This precision Spectroscopic Technique holds promise for the future development of high-throughput screening for plant phenotyping and the quantification of biologically or commercially relevant molecules, such as antioxidants and pigments.
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fast cars engineering a laser Spectroscopic Technique for rapid identification of bacterial spores
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Marlan O. Scully, George W Kattawar, Robert P Lucht, T Opatrny, H S Pilloff, Aleksander Rebane, Alexei V Sokolov, Mohammad Suhail ZubairyAbstract:Airborne contaminants, e.g., bacterial spores, are usually analyzed by time-consuming microscopic, chemical, and biological assays. Current research into real-time laser Spectroscopic detectors of such contaminants is based on e.g., resonance fluorescence. The present approach derives from recent experiments in which atoms and molecules are prepared by one (or more) coherent laser(s) and probed by another set of lasers. However, generating and using maximally coherent oscillation in macromolecules having an enormous number of degrees of freedom is challenging. In particular, the short dephasing times and rapid internal conversion rates are major obstacles. However, adiabatic fast passage Techniques and the ability to generate combs of phase-coherent femtosecond pulses provide tools for the generation and utilization of maximal quantum coherence in large molecules and biopolymers. We call this Technique FAST CARS (femtosecond adaptive Spectroscopic Techniques for coherent anti-Stokes Raman spectroscopy), and the present article proposes and analyses ways in which it could be used to rapidly identify preselected molecules in real time.
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fast cars engineering a laser Spectroscopic Technique for rapid identification of bacterial spores
arXiv: Optics, 2002Co-Authors: Marlan O. Scully, George W Kattawar, Robert P Lucht, T Opatrny, H S Pilloff, Aleksander Rebane, Alexei V Sokolov, Mohammad Suhail ZubairyAbstract:Airborne contaminants, e.g., bacterial spores, are usually analyzed by time consuming microscopic, chemical and biological assays. Current research into real time laser Spectroscopic detectors of such contaminants is based on e.g. resonant Raman spectroscopy. The present approach derives from recent experiments in which atoms and molecules are prepared by one (or more) coherent laser(s) and probed by another set of lasers. The connection with previous studies based on "Coherent Anti-Stokes Raman Spectroscopy" (CARS) is to be noted. However generating and utilizing maximally coherent oscillation in macromolecules having an enormous number of degrees of freedom is much more challenging. This extension of the CARS Technique is called FAST CARS (Femtosecond Adaptive Spectroscopic Techniques for Coherent Anti-Stokes Raman Spectroscopy), and the present paper proposes and analyses ways in which it could be used to rapidly identify pre-selected molecules in real time.
M Koch - One of the best experts on this subject based on the ideXlab platform.
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terahertz spectroscopy and imaging modern Techniques and applications
Laser & Photonics Reviews, 2011Co-Authors: Peter Uhd Jepsen, David G Cooke, M KochAbstract:Over the past three decades a new Spectroscopic Technique with unique possibilities has emerged. Based on coherent and time-resolved detection of the electric field of ultrashort radiation bursts in the far-infrared, this Technique has become known as terahertz time-domain spectroscopy (THz-TDS). In this review article the authors describe the Technique in its various implementations for static and time-resolved spectroscopy, and illustrate the performance of the Technique with recent examples from solid-state physics and physical chemistry as well as aqueous chemistry. Examples from other fields of research, where THz Spectroscopic Techniques have proven to be useful research tools, and the potential for industrial applications of THz Spectroscopic and imaging Techniques are discussed.
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terahertz spectroscopy and imaging modern Techniques and applications
Laser & Photonics Reviews, 2011Co-Authors: Peter Uhd Jepsen, David G Cooke, M KochAbstract:Over the past three decades a new Spectroscopic Technique with unique possibilities has emerged. Based on coherent and time-resolved detection of the electric field of ultrashort radiation bursts in the far-infrared, this Technique has become known as terahertz time-domain spectroscopy (THz-TDS). In this review article the authors describe the Technique in its various implementations for static and time-resolved spectroscopy, and illustrate the performance of the Technique with recent examples from solid-state physics and physical chemistry as well as aqueous chemistry. Examples from other fields of research, where THz Spectroscopic Techniques have proven to be useful research tools, and the potential for industrial applications of THz Spectroscopic and imaging Techniques are discussed.
Mohammad Suhail Zubairy - One of the best experts on this subject based on the ideXlab platform.
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fast cars engineering a laser Spectroscopic Technique for rapid identification of bacterial spores
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Marlan O. Scully, George W Kattawar, Robert P Lucht, T Opatrny, H S Pilloff, Aleksander Rebane, Alexei V Sokolov, Mohammad Suhail ZubairyAbstract:Airborne contaminants, e.g., bacterial spores, are usually analyzed by time-consuming microscopic, chemical, and biological assays. Current research into real-time laser Spectroscopic detectors of such contaminants is based on e.g., resonance fluorescence. The present approach derives from recent experiments in which atoms and molecules are prepared by one (or more) coherent laser(s) and probed by another set of lasers. However, generating and using maximally coherent oscillation in macromolecules having an enormous number of degrees of freedom is challenging. In particular, the short dephasing times and rapid internal conversion rates are major obstacles. However, adiabatic fast passage Techniques and the ability to generate combs of phase-coherent femtosecond pulses provide tools for the generation and utilization of maximal quantum coherence in large molecules and biopolymers. We call this Technique FAST CARS (femtosecond adaptive Spectroscopic Techniques for coherent anti-Stokes Raman spectroscopy), and the present article proposes and analyses ways in which it could be used to rapidly identify preselected molecules in real time.
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fast cars engineering a laser Spectroscopic Technique for rapid identification of bacterial spores
arXiv: Optics, 2002Co-Authors: Marlan O. Scully, George W Kattawar, Robert P Lucht, T Opatrny, H S Pilloff, Aleksander Rebane, Alexei V Sokolov, Mohammad Suhail ZubairyAbstract:Airborne contaminants, e.g., bacterial spores, are usually analyzed by time consuming microscopic, chemical and biological assays. Current research into real time laser Spectroscopic detectors of such contaminants is based on e.g. resonant Raman spectroscopy. The present approach derives from recent experiments in which atoms and molecules are prepared by one (or more) coherent laser(s) and probed by another set of lasers. The connection with previous studies based on "Coherent Anti-Stokes Raman Spectroscopy" (CARS) is to be noted. However generating and utilizing maximally coherent oscillation in macromolecules having an enormous number of degrees of freedom is much more challenging. This extension of the CARS Technique is called FAST CARS (Femtosecond Adaptive Spectroscopic Techniques for Coherent Anti-Stokes Raman Spectroscopy), and the present paper proposes and analyses ways in which it could be used to rapidly identify pre-selected molecules in real time.
