Detection of doubly-deuterated methanol in the solar-type protostar IRAS 16293-2422

By B. Parise, Cecilia Ceccarelli, A. Tielens, E. Herbst, Bertrand Lefloch, E. Caux, A. Castets, I. Mukhopadhyay, L. Pagani, L. Loinard. 2002

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We report the first detection of doubly-deuterated methanol (CHD2OH), as well as firm detections of the two singly-deuterated isotopomers of methanol (CH2DOH and CH3OD), towards the solar-type protostar IRAS 16293 2422. From the present multifrequency observations, we derive the following abundance ratios: (CHD 2OH)=(CH3OH)= 0:2 0:1, (CH2DOH)=(CH3OH)= 0:9 0:3, (CH3OD)=(CH3OH)= 0:04 0:02. The total abundance of the deuterated forms of methanol is greater than that of its normal hydrogenated counterpart in the circumstellar material of IRAS 16293 2422, a circumstance not previously encountered. Formaldehyde, which is thought to be the chemical precursor of methanol, possesses a much lower fraction of deuterated isotopomers (20%) with respect to the main isotopic form in IRAS 16293 2422. The observed frac- tionation of methanol and formaldehyde provides a severe challenge to both gas-phase and grain-surface models of deuteration. Two examples of the latter model are roughly in agreement with our observations of CHD2OH and CH2DOH if the accreting gas has a large (0.2-0.3) atomic D/H ratio. However, no gas-phase model predicts such a high atomic D/H ratio, and hence some key ingredient seems to be missing.

Subfields: Astronomy and Astrophysics, Inorganic Chemistry, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/016d27e8e91cb835b9e49b77df02849ee428d2d8

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Citations in the corpus

Enhanced Deuterium Fractionation in Dense Interstellar Cores Resulting from Multiply Deuterated H3+ (2003, background): “One of these protostars, IRAS 16293 2422, also has a total abundance of deuterated methanol that actually exceeds that of the main isotopomer (Parise et al. 2002).”
Exploring Molecular Complexity with ALMA (EMoCA): Deuterated complex organic molecules in Sagittarius B2(N2) (2015, methodology): “We compared theSµ2 values listed in Table 1 of Parise et al. (2002), which were also used in Parise et al. (2006), with thecurrent Article number, page 9 of 71 A&A proofs:manuscript no. aa27268aph Fig.”
Astrochemistry and compositions of planetary systems (2020, background): “CH3OH and 16 organics forming from CH3OH should have higher levels of deuteration than H2O, and this is indeed observed (Parise et al. 2002; Coutens et al. 2012; Persson et al. 2014; Taquet et al. 2019).”
What Is the Total Deuterium Abundance in the Local Galactic Disk? (2006, background): “…et al. (2004) point out that deuterium fractionations (the ratio of deuterated molecules to undeuterated molecules) for simple molecular species are typically 0.01 to 0.1 (e.g., Markwick, Charnley & Millar 2001) and higher deuterium fractionations have been measured (e.g., Parise et al. 2002).”
The chemistry of multiply deuterated species in cold, dense interstellar cores (2004, methodology): “These include D2CO (Loinard et al. 2001, 2002; Ceccarelli 2002; Ceccarelli et al. 2002), CH2DOH (Parise et al. 2002), NH2D (Saito et al. 2000; Hatchell 2003) and H2D+ (Caselli et al. 2003).”
The composition of ices in comet C/1995 O1 (Hale-Bopp) from radio spectroscopy (2004, methodology): “For CH2DOH we also used a list of transitions provided by Herbst (pers. comm.), described in Parise et al. (2002).”
Molecular inventories and chemical evolution of low-mass protostellar envelopes (2003, background): “…in terms of the chemistry of its protostellar envelope (see, e.g., Blake et al. 1994; van Dishoeck et al. 1995; Ceccarelli et al. 1998, 2000a,b; Schöier et al. 2002; Parise et al. 2002; Cazaux et al. 2003), because of its rich spectrum and its warm inner region where ices have evaporated.”
Our astrochemical heritage (2012, background): “HDCO, D2CO and CH2DOH have been detected in pre-stellar cores ([24]; [41]), while doubly and triply deuterated methanol have been detected in the envelope of young stellar objects ([343]; [340], see §5).”
Testing grain surface chemistry : a survey of deuterated formaldehyde and methanol in low-mass Class 0 protostars (2006, methodology): “Three years ago, doubly-deuterated methanol was detected towards the low-mass protostar IRAS16293 (CHD2OH/CH3OH ∼ 20%, Parise et al. 2002), basically confirming the grain chemistry scheme.”
First detection of triply-deuterated methanol (2003, methodology): “This value is nearly 3 times higher than the column density used by Parise et al. (2002), inferred from CH3OH observations from van Dishoeck et al. (1985).”
Complex Molecules in the Hot Core of the Low-Mass Protostar NGC 1333 IRAS 4A (2004, background): “…al. 2000a), high abundances of hydrides (CH3OH, H2CO, H2O: Ceccarelli et al. 2000a, b; Schöier et al. 2002), high deuteration levels (> 10%: Ceccarelli et al. 1998, 2001; Parise et al. 2002; Roberts et al. 2002), and complex molecules (HCOOCH3, HCOOH, CH3OCH3, CH3CN, C2H5CN: Cazaux et al. 2003).”
Molecular Evolution in Collapsing Prestellar Cores. III. Contraction of a Bonnor-Ebert Sphere (2004, background): “…multi-deuterated species have been detected in prestellar and protostellar cores, and their relative abundances to normal isotopomers, known as D/H ratios, found to be very high (10−3 − 10−1) (van der Tak et al. 2002; Lis et al. 2002; Parise et al. 2002; Bacmann et al. 2003; Parise et al. 2004).”
The Hot Core around the Low-Mass Protostar IRAS 16293–2422: Scoundrels Rule! (2003, background): “The warm gas also shows high levels of deuteration characteristic of a chemical history at much lower temperatures, including doubly deuterated species such as D2CO and CHD2OH (Ceccarelli et al. 1998, 2001; Parise et al. 2002).”