Detection of N<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Molecules in the Interstellar Medium by Their Microwave Emission

Cheung, Alvin; Rank, D. M.; Townes, C. H.; Thornton, D.; Welch, W. J.

doi:10.1103/physrevlett.21.1701

Cited by 409 publications

(153 citation statements)

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“…Ammonia (NH3) was the first polyatomic molecule to be detected in the interstellar medium (ISM) by Cheung et al (1968). NH3 is an ubiquitous molecule in the ISM and an invaluable probe of the physical conditions thanks to its many observable transitions that are sensitive to excitation conditions.…”

Section: Introductionmentioning

confidence: 99%

Collisional excitation of NH3 by atomic and molecular hydrogen

Bouhafs

Rist

Daniel

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We report extensive theoretical calculations on the rotation-inversion excitation of interstellar ammonia (NH 3 ) due to collisions with atomic and molecular hydrogen (both para-and ortho-H 2 ). Close-coupling calculations are performed for total energies in the range 1-2000 cm −1 and rotational cross sections are obtained for all transitions among the lowest 17 and 34 rotation-inversion levels of ortho-and para-NH 3 , respectively. Rate coefficients are deduced for kinetic temperatures up to 200 K. Propensity rules for the three colliding partners are discussed and we also compare the new results to previous calculations for the spherically symmetrical He and para-H 2 projectiles. Significant differences are found between the different sets of calculations. Finally, we test the impact of the new rate coefficients on the calibration of the ammonia thermometer. We find that the calibration curve is only weakly sensitive to the colliding partner and we confirm that the ammonia thermometer is robust.

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Section: Introductionmentioning

confidence: 99%

Collisional excitation of NH3 by atomic and molecular hydrogen

Bouhafs

Rist

Daniel

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…For example, the reaction between OH and NH 3 (another abundant molecule in space [24]) has a weakly bound pre-reactive complex (6.6 kJ mol -1 ) and a barrier to reaction (12.9 kJ mol -1 ), and the rate coefficient is small at room temperature, displaying a normal Arrhenius dependence at higher temperatures [25]. Calculations using MESMER show that, as in the methanol case, the reaction of OH with NH 3 increases rapidly at very low temperatures due to the weakly bound complex/QMT mechanism, and consistent with preliminary measurements [26].…”

Section: Discussionmentioning

confidence: 99%

Accelerated chemistry in the reaction between the hydroxyl radical and methanol at interstellar temperatures facilitated by tunnelling

et al. 2013

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Understanding the abundances of molecules observed in dense interstellar clouds requires knowledge of the rates of gas phase reactions between two neutral species. However, reactions possessing an activation barrier were considered too slow to play any important role at the low temperatures in these clouds. Here we show that despite the presence of a barrier the rate coefficient for the reaction between the hydroxyl radical (OH) and methanol, one of the most abundant organic molecules in space, is almost two orders of magnitude larger at 63K than previously measured at ~200K. We also observe formation of the methoxy radical product that was recently detected in space. These results are interpreted through the formation of a hydrogen-bonded complex that is sufficiently long-lived to undergo quantum mechanical tunnelling to form products. We postulate that this tunnelling

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“…These lines provided the socalled "ladder" giving multiple yet predictive features for unique molecular detection. Within six years, ammonia, water, and formaldehyde [19][20][21] were detected toward the galactic center (Saggitarius B2) and other sources. Precise experimental rotational data for these known molecules was already referenced making comparison to observation straightforward and unequivocal.…”

Section: The Origins Of Astrochemistrymentioning

confidence: 99%

Quantum astrochemical spectroscopy

Fortenberry

2016

Int J of Quantum Chemistry

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In this review, the origins of astrochemistry and the initial applications of quantum chemistry to the discovery of new molecules in space are discussed. Furthermore, more recent successes and failures of quantum astrochemistry are explored. Finally, the application of quantum chemistry to the chemical study of space is driving developments in large-scale computational science. Consequently, cloud computing and large molecule computations are discussed. Astrochemistry is a natural application of quantum chemistry. The ability to analyze routinely and completely the structural, spectroscopic, and electronic properties of any given molecule, regardless of its laboratory stability, make this tool a necessary component for astrochemical analysis. The sizes of the computations scaling with the number of electrons and degrees-of-freedom can become limiting, but proper choices of methods can provide unique insights. The chemistry of the Earth is a small snapshot of the chemistries available in the universe at large, and the flexibility inherent within computation make quantum chemistry an excellent driver of new knowledge in fundamental molecular science as well as in astrophysics.

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Detection of NH3Molecules in the Interstellar Medium by Their Microwave Emission

Cited by 409 publications

References 1 publication

Collisional excitation of NH3 by atomic and molecular hydrogen

Collisional excitation of NH3 by atomic and molecular hydrogen

Accelerated chemistry in the reaction between the hydroxyl radical and methanol at interstellar temperatures facilitated by tunnelling

Quantum astrochemical spectroscopy

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