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Emmanuel Momjian - One of the best experts on this subject based on the ideXlab platform.
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the Zeeman Effect in the 44 ghz class i methanol maser line toward dr21 oh
The Astrophysical Journal, 2017Co-Authors: Emmanuel Momjian, A P SarmaAbstract:We report detection of the Zeeman Effect in the 44 GHz Class I methanol maser line, toward the star-forming region DR21(OH). In a 219 Jy beam−1 maser centered at an LSR velocity of 0.83 km s−1, we find a 20-σ detection of zB los = 53.5 ± 2.7 Hz. If 44 GHz methanol masers are excited at n ~ 107–8 cm−3, then the B versus n 1/2 relation would imply, from comparison with Zeeman Effect detections in the CN(1 − 0) line toward DR21(OH), that magnetic fields traced by 44 GHz methanol masers in DR21(OH) should be ~10 mG. Combined with our detected zB los = 53.5 Hz, this would imply that the value of the 44 GHz methanol Zeeman splitting factor z is ~5 Hz mG−1. Such small values of z would not be a surprise, as the methanol molecule is non-paramagnetic, like H2O. Empirical attempts to determine z, as demonstrated, are important because there currently are no laboratory measurements or theoretically calculated values of z for the 44 GHz CH3OH transition. Data from observations of a larger number of sources are needed to make such empirical determinations robust.
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the Zeeman Effect in the 44 ghz class i methanol maser line toward dr21 oh
arXiv: Astrophysics of Galaxies, 2016Co-Authors: Emmanuel Momjian, A P SarmaAbstract:We report the detection of the Zeeman Effect in the 44 GHz Class I methanol maser line toward the star forming region DR21(OH). In a 219 Jy/beam maser centered at an LSR velocity of 0.83 km s$^{-1}$, we find a 20-$\sigma$ detection of $zB_{\text{los}} = 53.5 \pm 2.7$ Hz. If 44 GHz methanol masers are excited at $n \sim 10^{7-8}$ cm$^{-3}$, then the $B~vs.~n^{1/2}$ relation would imply from comparison with Zeeman Effect detections in the CN($1-0$) line toward DR21(OH) that magnetic fields traced by 44 GHz methanol masers in DR21(OH) should be $\sim$10 mG. Together with our detected $zB_{\text{los}} = 53.5$ Hz, this would imply that the value of the 44 GHz methanol Zeeman splitting factor $z$ is $\sim$5 Hz mG$^{-1}$. Such small values of $z$ would not be a surprise, as the methanol molecule is non paramagnetic, like H$_2$O. Empirical attempts to determine $z$, as demonstrated, are important because currently there are no laboratory measurements or theoretically calculated values of $z$ for the 44 GHz methanol transition. Data from observations of a larger number of sources are needed to make such empirical determinations robust.
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very large array detection of the 36 ghz Zeeman Effect in dr21w revisited
The Astrophysical Journal, 2012Co-Authors: Emmanuel Momjian, L O Sjouwerman, Vincent L FishAbstract:We report on the observation of the 36 GHz methanol maser line in the star-forming region DR21W to accurately measure the Zeeman Effect. The Zeeman signature reported by Fish et al. became suspicious after an instrumental Effect was discovered in the early days of the commissioning of the Very Large Array Wide-band Digital Architecture correlator. We conclude that the previously reported magnetic field strength of 58 mG (1.7 Hz mG–1/z) is instrumental in nature and thus incorrect. With the improved performance of the array, we now deduce a 3σ limit of –4.7 to +0.4 mG (1.7 Hz mG–1/z) for the line-of-sight component of the magnetic field strength in DR21W.
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very large array detection of the 36 ghz Zeeman Effect in dr21w revisited
arXiv: Astrophysics of Galaxies, 2012Co-Authors: Emmanuel Momjian, L O Sjouwerman, Vincent L FishAbstract:We report on the observation of the 36 GHz methanol maser line in the star forming region DR21W to accurately measure the Zeeman Effect. The reported Zeeman signature by Fish et al. (2011) became suspicious after an instrumental Effect was discovered in the early days of the Very Large Array Wide-band Digital Architecture (WIDAR) correlator commissioning. We conclude that the previously reported magnetic field strength of 58 mG ((1.7 Hz/mG)/z) is instrumental in nature and thus incorrect. With the improved performance of the array, we now deduce a 3 sigma limit of -4.7 to +0.4 mG ((1.7 Hz/mG)/z) for the line-of-sight component of the magnetic field strength in DR21W.
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discovery of the Zeeman Effect in the 44 ghz class i methanol ch3oh maser line
The Astrophysical Journal, 2011Co-Authors: A P Sarma, Emmanuel MomjianAbstract:We report the discovery of the Zeeman Effect in the 44?GHz Class I methanol (CH3OH) maser line. The observations were carried out with 22 antennas of the Expanded Very Large Array toward a star-forming region in OMC-2. Based on our adopted Zeeman splitting factor of z = 1.0 Hz mG-1, we detect a line-of-sight magnetic field of 18.4 ? 1.1 mG toward this source. Since such 44?GHz CH3OH masers arise from shocks in the outflows of star-forming regions, we can relate our measurement of the post-shock magnetic field to field strengths indicated by species tracing pre-shock regions, and thus characterize the large-scale magnetic field. Moreover, since Class I masers trace regions more remote from the star-forming core than Class II masers, and possibly earlier phases, magnetic fields detected in 6.7?GHz Class II and 36 and 44?GHz Class I methanol maser lines together offer the potential of providing a more complete picture of the magnetic field. This motivates further observations at high angular resolution to find the positional relationships between Class I and Class II masers, and masers at various frequencies within each category. In particular, CH3OH masers are widespread in high- as well as intermediate-mass star-forming regions, and our discovery provides a new method of studying the magnetic field in such regions, by observing small physical scales that are not accessible by any other lines.
Bernhard Welz - One of the best experts on this subject based on the ideXlab platform.
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investigation of chemical modifiers for the determination of lead in fertilizers and limestone using graphite furnace atomic absorption spectrometry with Zeeman Effect background correction and slurry sampling
Spectrochimica Acta Part B: Atomic Spectroscopy, 2014Co-Authors: Bernhard Welz, Aline R Borges, Emilene M Becker, Morgana B Dessuy, Maria Goreti R ValeAbstract:Abstract In this work, chemical modifiers in solution (Pd/Mg, NH 4 H 2 PO 4 and NH 4 NO 3 /Pd) were compared with permanent modifiers (Ir and Ru) for the determination of lead in fertilizer and limestone samples using slurry sampling and graphite furnace atomic absorption spectrometry with Zeeman-Effect background correction. The analytical line at 283.3 nm was used due to some spectral interference observed at 217.0 nm. The NH 4 H 2 PO 4 was abandoned due to severe spectral interference even at the 283.3-nm line. For Pd/Mg and NH 4 NO 3 /Pd the optimum pyrolysis and atomization temperatures were 900 °C and 1900 °C, respectively. For Ru and Ir, the integrated absorbance signal was stable up to pyrolysis temperatures of 700 °C and 900 °C, respectively, and up to atomization temperature of 1700 °C. The limit of detection (LOD) was 17 ng g − 1 using Pd/Mg and 29 ng g − 1 using NH 4 NO 3 /Pd. Among the permanent modifiers investigated, the LOD was 22 ng g − 1 Pb for Ir and 10 ng g − 1 Pb for Ru. The accuracy of the method was evaluated using the certified reference material NIST SRM 695. Although Ru provided lower LOD, which can be attributed to a lower blank signal, only the modifiers in solution showed concordant values of Pb concentration for the NIST SRM 695 and the most of analyzed samples. Moreover, the Pd/Mg modifier provided the highest sensitivity and for this reason it is more suitable for the determination of Pb in fertilizers samples in slurry; besides this it presented a better signal-to-noise ratio than NH 4 NO 3 /Pd.
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Optimization of analytical performance of a graphite furnace atomic absorption spectrometer with Zeeman-Effect background correction using variable magnetic field strength☆
Spectrochimica Acta Part B: Atomic Spectroscopy, 2003Co-Authors: Heike Gleisner, Klaus Eichardt, Bernhard WelzAbstract:Abstract This paper describes a graphite furnace atomic absorption spectrometer of the third generation with Zeeman-Effect background correction and variable magnetic field strength. Compared to earlier generations it is focused on magnetic field strength control and technical and analytical performance parameters. The Zeeman ratios for 10 elements at different magnetic field strengths were determined. The capability of increasing the magnetic field strength up to a maximum of 1.0 T allows the analytical sensitivity for Cu to be improved by up to 38%, resulting in an enhanced Zeeman ratio, and two-folds increase of the linear working range. Alternatively, the introduction of the 3-field mode–measurement at zero, maximum and a medium magnetic field strength – allows the sensitivity to be adapted for higher analyte concentrations. With this mode, Cu, Fe and Zn were determined in serum, with analyte contents in a concentration range common for flame atomic absorption spectrometry. The results were in good agreement with the expected values. The dynamic mode combines the sensitive measurement mode of graphite furnace atomic absorption spectrometry with the reduced-sensitivity 3-field mode. The present work demonstrates how this mode enables to extend calibration over 3 orders of magnitude for Pb.
A P Sarma - One of the best experts on this subject based on the ideXlab platform.
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the Zeeman Effect in the 44 ghz class i methanol maser line toward dr21 oh
The Astrophysical Journal, 2017Co-Authors: Emmanuel Momjian, A P SarmaAbstract:We report detection of the Zeeman Effect in the 44 GHz Class I methanol maser line, toward the star-forming region DR21(OH). In a 219 Jy beam−1 maser centered at an LSR velocity of 0.83 km s−1, we find a 20-σ detection of zB los = 53.5 ± 2.7 Hz. If 44 GHz methanol masers are excited at n ~ 107–8 cm−3, then the B versus n 1/2 relation would imply, from comparison with Zeeman Effect detections in the CN(1 − 0) line toward DR21(OH), that magnetic fields traced by 44 GHz methanol masers in DR21(OH) should be ~10 mG. Combined with our detected zB los = 53.5 Hz, this would imply that the value of the 44 GHz methanol Zeeman splitting factor z is ~5 Hz mG−1. Such small values of z would not be a surprise, as the methanol molecule is non-paramagnetic, like H2O. Empirical attempts to determine z, as demonstrated, are important because there currently are no laboratory measurements or theoretically calculated values of z for the 44 GHz CH3OH transition. Data from observations of a larger number of sources are needed to make such empirical determinations robust.
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the Zeeman Effect in the 44 ghz class i methanol maser line toward dr21 oh
arXiv: Astrophysics of Galaxies, 2016Co-Authors: Emmanuel Momjian, A P SarmaAbstract:We report the detection of the Zeeman Effect in the 44 GHz Class I methanol maser line toward the star forming region DR21(OH). In a 219 Jy/beam maser centered at an LSR velocity of 0.83 km s$^{-1}$, we find a 20-$\sigma$ detection of $zB_{\text{los}} = 53.5 \pm 2.7$ Hz. If 44 GHz methanol masers are excited at $n \sim 10^{7-8}$ cm$^{-3}$, then the $B~vs.~n^{1/2}$ relation would imply from comparison with Zeeman Effect detections in the CN($1-0$) line toward DR21(OH) that magnetic fields traced by 44 GHz methanol masers in DR21(OH) should be $\sim$10 mG. Together with our detected $zB_{\text{los}} = 53.5$ Hz, this would imply that the value of the 44 GHz methanol Zeeman splitting factor $z$ is $\sim$5 Hz mG$^{-1}$. Such small values of $z$ would not be a surprise, as the methanol molecule is non paramagnetic, like H$_2$O. Empirical attempts to determine $z$, as demonstrated, are important because currently there are no laboratory measurements or theoretically calculated values of $z$ for the 44 GHz methanol transition. Data from observations of a larger number of sources are needed to make such empirical determinations robust.
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discovery of the Zeeman Effect in the 44 ghz class i methanol ch3oh maser line
The Astrophysical Journal, 2011Co-Authors: A P Sarma, Emmanuel MomjianAbstract:We report the discovery of the Zeeman Effect in the 44?GHz Class I methanol (CH3OH) maser line. The observations were carried out with 22 antennas of the Expanded Very Large Array toward a star-forming region in OMC-2. Based on our adopted Zeeman splitting factor of z = 1.0 Hz mG-1, we detect a line-of-sight magnetic field of 18.4 ? 1.1 mG toward this source. Since such 44?GHz CH3OH masers arise from shocks in the outflows of star-forming regions, we can relate our measurement of the post-shock magnetic field to field strengths indicated by species tracing pre-shock regions, and thus characterize the large-scale magnetic field. Moreover, since Class I masers trace regions more remote from the star-forming core than Class II masers, and possibly earlier phases, magnetic fields detected in 6.7?GHz Class II and 36 and 44?GHz Class I methanol maser lines together offer the potential of providing a more complete picture of the magnetic field. This motivates further observations at high angular resolution to find the positional relationships between Class I and Class II masers, and masers at various frequencies within each category. In particular, CH3OH masers are widespread in high- as well as intermediate-mass star-forming regions, and our discovery provides a new method of studying the magnetic field in such regions, by observing small physical scales that are not accessible by any other lines.
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discovery of the Zeeman Effect in the 44 ghz class i methanol maser line
arXiv: Astrophysics of Galaxies, 2011Co-Authors: A P Sarma, Emmanuel MomjianAbstract:We report the discovery of the Zeeman Effect in the 44 GHz Class I methanol maser line. The observations were carried out with 22 antennas of the EVLA toward a star forming region in OMC-2. Based on our adopted Zeeman splitting factor of z = 1.0 Hz/mG, we detect a line of sight magnetic field of 18.4 +/- 1.1 mG toward this source. Since such 44 GHz methanol masers arise from shocks in the outflows of star forming regions, we can relate our measurement of the post-shock magnetic field to field strengths indicated by species tracing pre-shock regions, and thus characterize the large scale magnetic field. Moreover, since Class I masers trace regions more remote from the star forming core than Class II masers, and possibly earlier phases, magnetic fields detected in 6.7 GHz Class II and 36 GHz and 44 GHz Class I methanol maser lines together offer the potential of providing a more complete picture of the magnetic field. This motivates further observations at high angular resolution to find the positional relationships between Class I and Class II masers, and masers at various frequencies within each category. In particular, methanol masers are widespread in high- as well as intermediate-mass star forming regions, and our discovery provides a new method of studying the magnetic field in such regions, by observing small physical scales that are not accessible by any other lines.
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detection of the Zeeman Effect in the 36 ghz class i ch 3 oh maser line with the evla
The Astrophysical Journal, 2009Co-Authors: A P Sarma, Emmanuel MomjianAbstract:We report the first detection of the Zeeman Effect in the 36 GHz Class I CH{sub 3}OH maser line. The observations were carried out with 13 antennas of the EVLA toward the high mass star-forming region M8E. Based on our adopted Zeeman splitting factor of z = 1.7 Hz mG{sup -1}, we detect a line-of-sight magnetic field of -31.3 +- 3.5 mG and 20.2 +- 3.5 mG to the northwest and southeast of the maser line peak, respectively. This change in sign over a 1300 AU size scale may indicate that the masers are tracing two regions with different fields, or that the same field curves across the regions where the masers are being excited. The detected fields are not significantly different from the magnetic fields detected in the 6.7 GHz Class II CH{sub 3}OH maser line, indicating that CH{sub 3}OH masers may trace the large-scale magnetic field, or that the magnetic field remains unchanged during the early evolution of star-forming regions. Given what is known about the densities at which 36 GHz CH{sub 3}OH masers are excited, we find that the magnetic field is dynamically significant in the star-forming region.
Laurentius Windholz - One of the best experts on this subject based on the ideXlab platform.
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Zeeman Effect of weak la i lines investigated by the use of optogalvanic spectroscopy
Journal of Quantitative Spectroscopy & Radiative Transfer, 2017Co-Authors: ł M Sobolewski, Laurentius Windholz, J KwelaAbstract:Abstract New Lande- g J factors of 35 energy levels of La I, found from investigations of 40 spectral lines in the wavelength range 562.959÷609.537 nm, were determined. As a source of free La atoms a hollow cathode discharge lamp was used. We monitored the signal of the optogalvanic Effect appearing when a laser beam is passing through the hollow cathode. Spectra were recorded in the presence of a magnetic field of about 800 G produced by a permanent magnet, for two linear polarizations of the exciting laser light. Optogalvanic spectroscopy is a very sensitive method, so we were able to observe the Zeeman Effect of very weak atomic lines. In this way we have determined for the first time the Lande- g J factors for 35 recently found levels of neutral La. The Lande g J - factors for several other levels were reinvestigated.
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investigations of the Zeeman Effect of some 142nd ionic levels using collinear laser ion beam spectroscopy
Journal of Quantitative Spectroscopy & Radiative Transfer, 2015Co-Authors: S Werbowy, J Kwela, Harry Huhnermann, Laurentius WindholzAbstract:Abstract By performing laser excitation from the even 4f45d lower levels to the odd 4f46p and 4f35d2 upper levels of the neodymium ion 142Nd+, we have observed Zeeman splitting in an external magnetic field up to 330 G. We applied the high resolution spectroscopic method of collinear laser ion beam spectroscopy (CLIBS). With this method (unconventional for studying the Zeeman Effect) we recorded very well-resolved Zeeman structure patterns with line widths of order of 100 MHz, which is only sometimes the natural line width. The obtained experimental Lande factors are compared with earlier measurements and with theoretical calculations.
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Zeeman Effect of hyperfine resolved spectral lines of singly ionized praseodymium using collinear laser ion beam spectroscopy
Physical Review A, 2014Co-Authors: S Werbowy, J Kwela, N Anjum, Harry Huhnermann, Laurentius WindholzAbstract:Using the high-resolution spectroscopic method of collinear laser–ion-beam spectroscopy (CLIBS), the Zeeman Effect of singly ionized praseodymium spectral lines has been studied at relatively small magnetic fields up to 330 G. With this unusual method for studying the Zeeman Effect of ionic lines we recorded Zeeman-hyperfine structure patterns with clearly resolved components with linewidths as low as 60 MHz, which is only sometimes the natural linewidth. From the Zeeman patterns of 30 lines, improved Lande gJ factors were determined for 39 Pr II levels of the 4f 35d , 4f 25d2, and 4f 36p configurations.
S Werbowy - One of the best experts on this subject based on the ideXlab platform.
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investigations of the Zeeman Effect of some 142nd ionic levels using collinear laser ion beam spectroscopy
Journal of Quantitative Spectroscopy & Radiative Transfer, 2015Co-Authors: S Werbowy, J Kwela, Harry Huhnermann, Laurentius WindholzAbstract:Abstract By performing laser excitation from the even 4f45d lower levels to the odd 4f46p and 4f35d2 upper levels of the neodymium ion 142Nd+, we have observed Zeeman splitting in an external magnetic field up to 330 G. We applied the high resolution spectroscopic method of collinear laser ion beam spectroscopy (CLIBS). With this method (unconventional for studying the Zeeman Effect) we recorded very well-resolved Zeeman structure patterns with line widths of order of 100 MHz, which is only sometimes the natural line width. The obtained experimental Lande factors are compared with earlier measurements and with theoretical calculations.
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Zeeman Effect of hyperfine resolved spectral lines of singly ionized praseodymium using collinear laser ion beam spectroscopy
Physical Review A, 2014Co-Authors: S Werbowy, J Kwela, N Anjum, Harry Huhnermann, Laurentius WindholzAbstract:Using the high-resolution spectroscopic method of collinear laser–ion-beam spectroscopy (CLIBS), the Zeeman Effect of singly ionized praseodymium spectral lines has been studied at relatively small magnetic fields up to 330 G. With this unusual method for studying the Zeeman Effect of ionic lines we recorded Zeeman-hyperfine structure patterns with clearly resolved components with linewidths as low as 60 MHz, which is only sometimes the natural linewidth. From the Zeeman patterns of 30 lines, improved Lande gJ factors were determined for 39 Pr II levels of the 4f 35d , 4f 25d2, and 4f 36p configurations.
