The dissociative recombination of fluorocarbon ions: II. CF<sup>+</sup>

Novotny, Steffen; Mitchell, James B.; LeGarrec, J L; Florescu-Mitchell, A. I.; Rebrion-Rowe, C.; Svendsen, Annette; Ghazaly, M A El; Andersen, L. H.; Ehlerding, Anneli; Viggiano, A. A.; Hellberg, F.; Thomas, Richard; Zhaunerchyk, Vitali; Geppert, Wolf D.; Montaigne, H; Kamińska, Magdalena; Österdahl, Fabian; Larsson, Mats

doi:10.1088/0953-4075/38/10/006

Cited by 26 publications

(19 citation statements)

References 35 publications

(52 reference statements)

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“…It has been shown, however, that DR rate coefficients of diatomics can differ by large factors from alleged typical values. For example, for CF + Novotny et al (2005) measured a rate coefficient a factor of 4 lower than that commonly taken for the typical diatomic ion value. For this reason Neufeld et al (2012) have identified the DR rate coefficient of HCl + as an "urgently needed" parameter significantly affecting the uncertainty of chlorine-chemistry models.…”

Section: Introductionmentioning

confidence: 79%

DISSOCIATIVE RECOMBINATION MEASUREMENTS OF HCl⁺ USING AN ION STORAGE RING

Novotný

Becker

Buhr

et al. 2013

ApJ

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We have measured dissociative recombination of HCl + with electrons using a merged beams configuration at the heavy-ion storage ring TSR located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. We present the measured absolute merged beams recombination rate coefficient for collision energies from 0 to 4.5 eV. We have also developed a new method for deriving the cross section from the measurements. Our approach does not suffer from approximations made by previously used methods. The cross section was transformed to a plasma rate coefficient for the electron temperature range from T = 10 to 5000 K. We show that the previously used HCl + DR data underestimate the plasma rate coefficient by a factor of 1.5 at T = 10 K and overestimate it by a factor of 3.0 at T = 300 K. We also find that the new data may partly explain existing discrepancies between observed abundances of chlorine-bearing molecules and their astrochemical models.

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Section: Introductionmentioning

confidence: 79%

DISSOCIATIVE RECOMBINATION MEASUREMENTS OF HCl⁺ USING AN ION STORAGE RING

Novotný

Becker

Buhr

et al. 2013

ApJ

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“…Where no reliable DR data exist for diatomic molecules, astrochemical models commonly assume a "typical" rate coefficient of α di pl ≈ 2.0×10 −7 ×(300/T ) 0.5 cm 3 s −1 (Florescu- Mitchell & Mitchell 2006). As has been shown for CF + (Novotny et al 2005) and HCl + (Novotný et al 2013), α di pl does a poor job of matching experimentally derived rate coefficient α pl both in magnitude and temperature dependence. Taking the ratio of our new DR results to that commonly assumed we find α pl /α di pl = 1.9, 1.2, 0.9, 0.6, and 0.5 at T = 10, 30, 100, 300, and 1000 K, respectively.…”

Section: Plasma Rate Coefficientmentioning

confidence: 90%

DISSOCIATIVE RECOMBINATION MEASUREMENTS OF NH⁺USING AN ION STORAGE RING

Novotný

Berg

Bing

et al. 2014

ApJ

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We have investigated dissociative recombination (DR) of NH + with electrons using a merged beams configuration at the TSR heavy-ion storage ring located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. We present our measured absolute merged beams recombination rate coefficient for collision energies from 0 to 12 eV. From these data we have extracted a cross section which we have transformed to a plasma rate coefficient for the collisional plasma temperature range from T pl = 10 to 18000 K. We show that the NH + DR rate coefficient data in current astrochemical models are underestimated by up to a factor of ∼ 9. Our new data will result in predicted NH + abundances lower than calculated by present models. This is in agreement with the sensitivity limits of all observations attempting to detect NH + in interstellar clouds.In the cold ISM, such as in molecular clouds, the most abundant nitrogen-bearing species are expected to be N and N 2 (Langer & Graedel 1989). However, direct observation of these is difficult. Atomic N does not have any low-lying, fine-structure levels that can be populated at molecular cloud temperatures and N 2 lacks a dipole moment, which is needed to provide reasonably strong ro-vibrational transitions. Thus, observations of tracers such as NH, NH 2 , NH 3 , or N 2 H + must be used to infer the N and N 2 abundances through chemical models.Neutral nitrogen hydrides are widely seen in the ISM. Ammonia (NH 3 ) was first detected by Cheung et al. (1968). Later NH 2 and NH were identified by van Dishoeck et al. (1993) and Meyer & Roth (1991), respectively. The observed abundances, however, do not match predictions from astrochemical models. In diffuse interstellar clouds, observed abundance ratio for NH/NH 3 are ∼ 1.7 and for NH 3 /H ∼ 3.2 × 10 −9 . These cannot be simultaneously explained by existing chemical models. The models can fit either one of the observed values but then the other predicted ratio is a factor of 10 off from the observation (Persson et al. 2010). Similarly, in dark clouds the abundance ratio for NH/NH 3 is underpredicted by more than an order of magnitude (Hily-Blant et al. 2010). These discrepancies possibly originate from using incorrect reaction rate coefficients in the models.

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“…The reactions rates are k 1 = 7.2 × 10 −9 (T/300) −0.15 cm 3 s −1 (Neufeld et al 2005) and k 2 = 5.3 × 10 −8 (T/300) −0.8 cm 3 s −1 (Novotny et al 2005). The CF + photodissociation rate k pd is not known.…”

Section: Cfmentioning

confidence: 99%