Results 111 to 120 of about 49,075 (253)

Enigma of H 3 + in Diffuse Interstellar Clouds [PDF]

, 2003
H 3 + is of fundamental importance to interstellar chemistry both because it is a hydrogenic species (and >9O% of all nuclei in the universe are hydrogen nuclei; see Fig. 1) and because it serves as the universal protonator, initiating a chain of ion-neutral reactions that is responsible for the formation of most interstellar molecules.
Benjamin J. McCall, Takeshi Oka
openaire   +1 more source

Optical Spectroscopy of Galactic Cirrus Clouds: Extended Red Emission in the Diffuse Interstellar Medium [PDF]

, 1997
We present initial results from the first optical spectroscopic survey of high latitude Galactic cirrus clouds. The observed shape of the cirrus spectrum does not agree with that of scattered ambient Galactic starlight.
Arpad Szomoru, Boulanger F., de Vaucouleurs G., de Vaucouleurs G., de Vries C. P., Duley W. W., Duley W. W., Duley W. W., Heiles C., Hendecourt L., Mathis J. S., Mattila K., Mezger P. G., Perrin J.-M., Perrin J.-M., Puget J. L., Puragra Guhathakurta, Scott A. D., Stark R., Webster A.   +19 more
core   +3 more sources

Recent developments and applications of selected ion flow tube mass spectrometry (SIFT‐MS)

Mass Spectrometry Reviews, Volume 44, Issue 2, Page 101-134, March/April 2025.
Abstract Selected ion flow tube mass spectrometry (SIFT‐MS) is now recognized as the most versatile analytical technique for the identification and quantification of trace gases down to the parts‐per‐trillion by volume, pptv, range. This statement is supported by the wide reach of its applications, from real‐time analysis, obviating sample collection ...
David Smith, Patrik Španěl, Nicholas Demarais, Vaughan S. Langford, Murray J. McEwan   +4 more
wiley   +1 more source

H i Kinematics and the E(B − V)/N(H i) Ratio

The Astrophysical Journal
The λ 21 cm H i emission that is used to trace the gas-to-dust ratio at high Galactic latitudes has contributions from material beyond the Milky Way disk, with uncertain and likely subsolar metallicity and dust content.
Harvey Liszt
doaj   +1 more source

Preimpact Detection of Chelyabinsk‐Type Objects in the Thermal Infrared: Possibilities and Limitations

Advances in Astronomy, Volume 2025, Issue 1, 2025.
The Chelyabinsk meteor entered Earth’s atmosphere on 15 February 2013, producing a shock wave that injured about 1500 people and damaged thousands of buildings. Despite its relatively large size (∼20 m), the progenitor asteroid approached Earth undetected. Its apparent radiant was too close to the Sun for standard ground‐based near‐Earth asteroid (NEA)
Thomas Müller, Luca Conversi, Javier Licandro, Marco Delbo, Alan Fitzsimmons, Karri Muinonen, Marcel Popescu, Paolo Tanga, Richard Moissl, Michael Kueppers   +9 more
wiley   +1 more source

Phenyl Radical Activates Molecular Hydrogen Through Protium and Deuterium Tunneling

Angewandte Chemie International Edition, Volume 63, Issue 51, December 16, 2024.
Activating the strong H2 bond is typically reserved for transition metals, and only a few main group systems can tackle this challenge. Here, we explore a phenyl radical mediated pathway utilizing the photolysis of iodobenzene. The phenyl radical leverages the high C−H bond energy of the forming benzene to drive H2 activation.
Virinder Bhagat, Jan Meisner, Jan Philipp Wagner   +2 more
wiley   +1 more source

Silicate Extinction Profile Based on the Stellar Spectrum by Spitzer/IRS

The Astrophysical Journal
The 9.7 and 18 μ m interstellar spectral features, arising from the Si–O stretching and O–Si–O bending modes of amorphous silicate dust, are the strongest extinction features in the infrared.
Zhenzhen Shao, Biwei Jiang
doaj   +1 more source

The formation of molecules in diffuse interstellar clouds

The Astrophysical Journal, 1977
A chemical system involving carbon and hydrogen is used to obtain steady-state abundances of a number of molecules over a wide range of densities. The calculated CH abundance agrees well with the astronomical observations. For reasonable values of the rate coefficients, the present system of reactions cannot explain, simultaneously, the measured ...
G. F. Mitchell, P. J. Kuntz, J. L. Ginsburg   +2 more
openaire   +1 more source

Overtone Transition 2ν1 of HCO+ and HOC+: Origin, Radiative Lifetime, Collisional Quenching

ChemPhysChem, Volume 25, Issue 21, November 4, 2024.
The C−H/O−H stretch vibration overtone of one of the simplest molecular ion isomeric systems HCO+/HOC+ is studied in a cryogenic ion trap experiment. Moreover, our comprehensive “zero background” method enables the determination of radiative lifetimes and select quenching reaction rates at the same time.
Miguel Jiménez‐Redondo, Liliia Uvarova, Petr Dohnal, Miroslava Kassayová, Paola Caselli, Pavol Jusko   +5 more
wiley   +1 more source

The carbon abundance in diffuse interstellar clouds

The Astrophysical Journal, 1981
When N/sub H2/roughly-equal1-40 x 10/sup 19/ cm/sup -2/ in a given direction, or f equivalent 2N/sub H2//N/sub H/>10/sup -1.4/, the column densities of C I and H/sub 2/ are strongly correlated even though N/sub C/ /sub i/ and N/sub H/ are not. All or most of the observed C I in such directions is harbored by a single, predominantly molecular (H/sub 2/>>
openaire   +1 more source