scholarly journals Photoproduction of H3+ from gaseous methanol inside dense molecular clouds

2008 ◽  
Vol 4 (S251) ◽  
pp. 369-370
Author(s):  
S. Pilling ◽  
D. P. P. Andrade ◽  
A. C. F. Santos ◽  
H. M. Boechat-Roberty
Keyword(s):  
Cross Sections ◽  
Molecular Clouds ◽  
Mass Spectra ◽  
Column Density ◽  
X Rays ◽  
Alternative Source ◽  
X Ray ◽  
Flight Mass Spectrometry ◽  
Dense Molecular Cloud ◽  
Synchrotron Light

AbstractWe present experimental results obtained from photoionization and photodissociation processes of abundant interstellar methanol (CH3OH) as an alternative route for the production of H3+ in dense clouds. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS) employing soft X-ray and time-of-flight mass spectrometry. Mass spectra were obtained using the photoelectron-photoion coincidence techniques. Absolute averaged cross sections for the production of H3+ due to molecular dissociation of methanol by soft X-rays (C1s edge) were determined. The H3+'s photoproduction rate and column density were been estimated adopting a typical soft X-ray luminosity inside dense molecular and the observed column density of methanol. Assuming a steady state scenario, the highest column density value for the photoproduced H3+ was about 1011 cm2, which gives the ratio photoproduced/observed of about 0.05%, as in the case of dense molecular cloud AFGL 2591. Despite the small value, this represent a new and alternative source of H3+ into dense molecular clouds and it is not been considered as yet in interstellar chemistry models.

Destruction of C2H4O2 isomers in ice-phase by X-rays: Implication on the abundance of acetic acid and methyl formate in the interstellar medium

2017 ◽  
Vol 13 (S332) ◽  
pp. 418-424
Author(s):  
Marina G. Rachid ◽  
K. Faquine ◽  
S. Pilling
Keyword(s):  
Acetic Acid ◽  
Cross Sections ◽  
Methyl Formate ◽  
X Rays ◽  
Formation Cross Section ◽  
X Ray ◽  
Synchrotron Light ◽  
The Difference ◽  
Astrophysical Ices

AbstractC2H4O2 isomers, methyl formate (HCOOCH3), acetic acid (CH3COOH) and glycoaldehyde (HOCH2CHO), have been detected in a lot of sources in ISM. However, their abundances are very different, with methyl formate much more abundant than the other two isomers. This fact may be related to the different destruction by ionizing radiation of these molecules. The goal of this work is experimentally study the photodissociation processes of methyl formate and acetic acid ices when exposed to broadband soft X-ray from 6 up to 2000 eV. The experiments were performed coupled to the SGM beamline in the Brazilian Synchrotron Light Source (LNLS/CNPEM) at Campinas, Brazil. The simulated astrophysical ices (12K) were monitored throughout the experiment using infrared vibrational spectroscopy. The analysis of processed ices allowed the determination of the effective destruction cross sections of the parent molecules as well as the effective formation cross section of daughter molecular species. The relative abundance between acetic acid and methyl formate (NCH3COOH/NHCOOCH3) in different astronomical scenarios and their column density evolution in the presence of X-rays were calculated and our results suggests that such radiation field can be one of the factors that explain the difference in the isomers C2H4O2 abundances. We also quantified the daugther species after the establishment of a chemical equilibrium in the samples.

scholarly journals Destruction and multiple ionization of PAHs by X-rays in circumnuclear regions of AGNs

2019 ◽  
Vol 488 (1) ◽  
pp. 451-469 ◽  
Author(s):  
Thiago Monfredini ◽  
Heidy M Quitián-Lara ◽  
Felipe Fantuzzi ◽  
Wania Wolff ◽  
Edgar Mendoza ◽  
...  
Keyword(s):  
Cross Sections ◽  
Galactic Nuclei ◽  
X Rays ◽  
Flight Mass Spectrometry ◽  
Multiply Charged ◽  
Significant Difference ◽  
Astrophysical Objects ◽  
Polycyclic Aromatic ◽  
Synchrotron Light ◽  
Charged Ions

ABSTRACT The infrared signatures of polycyclic aromatic hydrocarbons (PAHs) are observed in a variety of astrophysical objects, including the circumnuclear medium of active galactic nuclei (AGNs). These are sources of highly energetic photons (0.2–10 keV), exposing the PAHs to a harsh environment. In this work, we examined experimentally the photoionization and photostability of naphthalene (C10H8), anthracene (C14H10), 2-methyl-anthracene (C14H9CH3), and pyrene (C16H10) upon interaction with photons of 275, 310, and 2500 eV. The measurements were performed at the Brazilian Synchrotron Light Laboratory using time-of-flight mass-spectrometry. We determined the absolute photoionization and photodissociation cross-sections as a function of the incident photon energy; the production rates of singly, doubly, and triply charged ions; and the molecular half-lives in regions surrounding AGNs. Even considering moderate X-ray optical depth values (τ = 4.45) due to attenuation by the dusty torus, the half-lives are not long enough to account for PAH detection. Our results suggest that a more sophisticated interplay between PAHs and dust grains should be present in order to circumvent molecular destruction. We could not see any significant difference in the half-life values by increasing the size of the PAH carbon backbone, NC, from 10 to 16. However, we show that the multiple photoionization rates are significantly greater than the single ones, irrespective of the AGN source. We suggest that an enrichment of multiply charged ions caused by X-rays can occur in AGNs.

scholarly journals The Mass Spectrum of Interstellar Clouds

1989 ◽  
Vol 120 ◽  
pp. 511-517
Author(s):  
John M. Dickey ◽  
R. W. Garwood
Keyword(s):  
Cross Sections ◽  
Molecular Clouds ◽  
Column Density ◽  
Unit Volume ◽  
Empirical Relationship ◽  
Line Of Sight ◽  
Interstellar Clouds ◽  
Absorption Studies ◽  
Low Latitudes ◽  
Diffuse Clouds

AbstractThe abundance of 21-cm absorption lines seen in surveys at high latitudes can be translated into a line of sight abundance of clouds vs. column density using an empirical relationship between temperature and optical depth. As VLA surveys of 21-cm absorption at low latitudes are now becoming available, it is possible to study the variation of this function with galactic radius. It is interesting to compare the abundance of these diffuse atomic clouds (with temperatures of 50 to 100 K and masses of 1 to 10 M⊙) to the abundance of molecular clouds. To do the latter we must make assumptions about cloud cross-sections in order to convert the line of sight abundance of diffuse clouds into a number per unit volume, and to convert from cloud column density to mass. The spectrum of diffuse clouds matches fairly well the spectrum of molecular clouds, although observationally there is a gap of several orders of magnitude in cloud mass. Optical absorption studies also agree well with the 21-cm results for clouds of column density a few times 1020 M⊙.

Rapid Quantitative Analysis by X-Ray Spectrometry

1971 ◽  
Vol 15 ◽  
pp. 164-175 ◽  
Author(s):  
Robert D. Giauque ◽  
Joseph M. Jaklevic
Keyword(s):  
Cross Sections ◽  
Fluorescence Analysis ◽  
Selective Excitation ◽  
Single Element ◽  
X Rays ◽  
Analysis Method ◽  
Yield Data ◽  
X Ray ◽  
Minimum Number ◽  
Sample Dilution

An x-ray fluorescence analysis method applicable to the case of fluorescent spectra excited with monoenergetic x-rays has been developed. The technique employs a minimum number of calibration steps using single element thin film standards and depends upon theoretical cross sections and fluorescent yield data to interpolate from element to element. The samples are treated as thin films and corrections for absorption effects are easily determined- Enhancement effects, if not negligible, are minimized by sample dilution techniques or by selective excitation.

Electron Vacancy Production in Near-symmetric Collisions of 100 MeV Copper Ions

1981 ◽  
Vol 34 (2) ◽  
pp. 155 ◽  
Author(s):  
HJ Hay ◽  
LF Pender ◽  
PB Treacy
Keyword(s):  
High Resolution ◽  
Cross Sections ◽  
Copper Ions ◽  
X Rays ◽  
X Ray ◽  
Rotational Coupling ◽  
Cu Ions ◽  
Electron Vacancy ◽  
Production Target ◽  
Detector Characteristic

With a high-resolution Si(Li) X-ray detector, characteristic K X rays have been detected with targets of Cr, Fe, Cu, Ge and Se ombarded by 100 MeV Cu ions, equilibrated by passing through carbon. Cross sections for X-ray production, target-to-projectile vacancy-sharing ratios and K, to K, ratios were measured and compared with predictions of molecular-coupling theories. The results show little greement with existing models based on rotational coupling in molecular-orbital states.

scholarly journals Measurement of Carbon Ion Photoabsorption Cross Sections Using Laser Plasmas

1990 ◽  
Vol 115 ◽  
pp. 53-56
Author(s):  
B. Wargelin ◽  
S.M. Kahn ◽  
W. Craig ◽  
R. London
Keyword(s):  
Cross Sections ◽  
Grazing Incidence ◽  
X Rays ◽  
Carbon Ion ◽  
X Ray ◽  
Laser Plasmas ◽  
X Ray Imaging ◽  
Low Temperature Plasmas ◽  
Ion Species ◽  
High Column

AbstractLaser plasmas are well-suited to studies of ionic photoabsorption because they can provide highly ionized, low temperature plasmas of high column density, as well as bright, compact continuum X-ray sources which can illuminate the plasma under study. In our experiment, continuum X-rays from a gold laser plasma are partially absorbed as they traverse a carbon plasma and are then dispersed by a grazing incidence reflection grating. An X-ray imaging camera records both the absorbed and unabsorbed spectra simultaneously for later computer analysis to determine the photoabsorption cross sections for each carbon ion species.

Measurement of L X-ray production cross sections and relative intensities of some lanthanide compounds depending on the temperature

2020 ◽  
Vol 108 (5) ◽  
pp. 415-423
Author(s):  
Esra Cinan ◽  
Bünyamin Aygün ◽  
M. I. Sayyed ◽  
Yüksel Özdemir
Keyword(s):  
Cross Sections ◽  
Full Width Half Maximum ◽  
Production Cross ◽  
Emission Spectra ◽  
X Rays ◽  
X Ray ◽  
Different Temperatures ◽  
Intensity Ratios ◽  
Annular Source

AbstractL X-ray intensity ratios for CeO2, Sm2(SO4)3, Ho2O3, and Yb2O3 compounds were experimentally investigated. The measurements were gauged following excitation by 59.54 keV γ-rays from a 100 mCi 241Am radioactive annular source at different temperatures in situ. Temperature change occurred between 50 °C and 400 °C. L X-ray emission spectra were obtained by using a solid-state Si(Li) X-ray detector. L X-ray production cross sections, intensity ratios, and full-width half maximum (FWHM) values for the compounds were determined by evaluating the emission spectra varying with the temperature. According to the results obtained, it was observed that Lβ1 X-rays were less influenced in comparison with Lα X-rays while Lα X-rays were also less influenced in comparison with Lβ2 X-rays.

Photon-Induced L-Shell X-Ray Production Cross Sections for Lanthanides at 59.54 keV

2017 ◽  
Vol 890 ◽  
pp. 223-226 ◽  
Author(s):  
Rıdvan Durak ◽  
Ferdi Akman ◽  
Abdulhalik Karabulut
Keyword(s):  
High Resolution ◽  
Cross Sections ◽  
Production Cross ◽  
Theoretical Data ◽  
Experimental Results ◽  
X Rays ◽  
X Ray ◽  
Reflection Geometry ◽  
Experimental Values ◽  
Annular Source

The Ll, Lα and Lβ X-ray production cross sections for Pr, Nd, Sm, Eu, Gd and Tb elements were determined using a reflection geometry. The excitation was performed with a 241Am radioactive annular source and the L X-rays emitted from targets were counted with a high-resolution Si (Li) detector. The experimental values were compared with other available experimental results and theoretical data. An agreement is observed between the measured and other experimental results or theoretical data.

Vacuum Ultraviolet Photoionization Mass Spectra and Cross-Sections for Volatile Organic Compounds at 10.5 eV

2007 ◽  
Vol 61 (8) ◽  
pp. 896-902 ◽  
Author(s):  
Nozomu Kanno ◽  
Kenichi Tonokura
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Cross Sections ◽  
Mass Spectra ◽  
Vacuum Ultraviolet ◽  
Single Photon ◽  
Photoionization Cross Section ◽  
Oxygenated Compounds ◽  
Flight Mass Spectrometry ◽  
Volatile Organic

Vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) has been applied to the detection of volatile organic compounds (VOCs), including aromatic, chlorinated, and oxygenated compounds. Photoionization mass spectra of 23 VOCs were measured using SPI-TOFMS at 10.5 eV (118 nm). The limits of detection of VOCs using SPI-TOFMS at 10.5 eV were estimated to be a few ppbv. The mass spectra of 20 VOCs exhibit only the parent ion and its isotopes' signals. The ionization processes of the VOCs were discussed on the basis of the reaction enthalpies predicted by the quantum chemical calculations. Absolute photoionization cross-sections for 23 VOCs, including 12 newly measured VOCs, at 10.5 eV were determined in comparison to the reported absolute photoionization cross-section of NO.

scholarly journals Development of a sticker sealed microfluidic device for in situ analytical measurements using synchrotron radiation

2021 ◽  
Author(s):  
ITAMAR NECKEL ◽  
Lucas F. de Castro ◽  
Flavia Callefo ◽  
Verônica Teixeira ◽  
Angelo Gobbi ◽  
...  
Keyword(s):  
Microfluidic Device ◽  
Green Energy ◽  
X Rays ◽  
Electrical Measurements ◽  
X Ray ◽  
Electrochemical Nucleation ◽  
Synchrotron Light

Abstract Shedding synchrotron light on microfluidic systems, exploring several contrasts in situ operando at the nanoscale, like X-ray fluorescence, diffraction, luminescence, and absorption, has the potential to reveal new properties and functionalities of materials across diverse areas, such as green energy, photonics, and nanomedicine. In this work, we present the micro-fabrication and characterization of a multifunctional polyester/glass sealed microfluidic device well-suited to combine with analytical X-ray techniques. The device consists of smooth microchannels patterned on glass, where three gold electrodes are deposited into the channels to serve in situ electrochemistry analysis or standard electrical measurements. It has been efficiently sealed through an ultraviolet-sensitive sticker-like layer based on a polyester film, and The burst pressure determined by pumping water through the microchannel(up to 0.22 MPa). Overall, the device has demonstrated exquisite chemical resistance to organic solvents, and its efficiency in the presence of biological samples (proteins) is remarkable. The device potentialities, and its high transparency to X-rays, have been demonstrated by taking advantage of the X-ray nanoprobe Carnaúba/Sirius/LNLS, by obtaining 2D X-ray nanofluorescence maps on the microchannel filled with water and after an electrochemical nucleation reaction. To wrap up, the microfluidic device characterized here has the potential to be employed in standard laboratory experiments as well as in situ and in vivo analytical experiments using a wide electromagnetic window, from infrared to X-rays, which could serve experiments in many branches of science.

Sign in / Sign up

Export Citation Format

Share Document