Person:
Bergner, Jennifer

Profile Picture

Email Address

AA Acceptance Date

Birth Date

Research Projects

Organizational Units

Job Title

Last Name

Bergner

First Name

Jennifer

Name

Bergner, Jennifer

Filters

20172

Settings

Author's Publications: search.filters.isAuthorOfPublication.9ebb2de0-7923-428c-8066-83d5bf19bd06

Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Publication
    Methanol Formation via Oxygen Insertion Chemistry in Ices
    (American Astronomical Society, 2017-08-09) Bergner, Jennifer; Oberg, Karin; Rajappan, Mahesh
    We present experimental constraints on the insertion of oxygen atoms into methane to form methanol in astrophysical ice analogs. In gas-phase and theoretical studies this process has previously been demonstrated to have a very low or nonexistent energy barrier, but the energetics and mechanisms have not yet been characterized in the solid state. We use a deuterium UV lamp filtered by a sapphire window to selectively dissociate O 2 within a mixture of O 2 :CH 4 and observe efficient production of CH 3 OH via O( 1 D) insertion. CH 3 OH growth curves are fit with a kinetic model, and we observe no temperature dependence of the reaction rate constant at temperatures below the oxygen desorption temperature of 25 K. Through an analysis of side products we determine the branching ratio of ice-phase oxygen insertion into CH 4 : ∼65% of insertions lead to CH 3 OH, with the remainder leading instead to H 2 CO formation. There is no evidence for CH 3 or OH radical formation, indicating that the fragmentation is not an important channel and that insertions typically lead to increased chemical complexity. CH 3 OH formation from O 2 and CH 4 diluted in a CO-dominated ice similarly shows no temperature dependence, consistent with expectations that insertion proceeds with a small or nonexistent barrier. Oxygen insertion chemistry in ices should therefore be efficient under low-temperature ISM-like conditions and could provide an important channel to complex organic molecule formation on grain surfaces in cold interstellar regions such as cloud cores and protoplanetary disk midplanes.
  • No Thumbnail Available
    Publication
    Complex Organic Molecules toward Embedded Low-mass Protostars
    (American Astronomical Society, 2017-06-02) Bergner, Jennifer; Oberg, Karin; Garrod, Robin; Graninger, Dawn
    Complex organic molecules (COMs) have been observed toward several low-mass young stellar objects (LYSOs). Small and heterogeneous samples have so far precluded conclusions on typical COM abundances, as well as the origin(s) of abundance variations between sources. We present observations toward 16 deeply embedded (Class 0/I) low-mass protostars using the IRAM 30 m telescope. We detect CH 2 CO, CH 3 CHO, CH 3 OCH 3 , CH 3 OCHO, CH 3 CN, HNCO, and HC 3 N toward 67%, 37%, 13%, 13%, 44%, 81%, and 75% of sources, respectively. Median column densities derived using survival analysis range between 6.0 × 10 10 cm −2 (CH 3 CN) and 2.4 × 10 12 cm −2 (CH 3 OCH 3 ), and median abundances range between 0.48% (CH 3 CN) and 16% (HNCO) with respect to CH 3 OH. Column densities for each molecule vary by about one order of magnitude across the sample. Abundances with respect to CH 3 OH are more narrowly distributed, especially for oxygen-bearing species. We compare observed median abundances with a chemical model for low-mass protostars and find fair agreement, although some modeling work remains to bring abundances higher with respect to CH 3 OH. Median abundances with respect to CH 3 OH in LYSOs are also found to be generally comparable to observed abundances in hot cores, hot corinos, and massive YSOs. Compared with comets, our sample is comparable for all molecules except HC 3 N and CH 2 CO, which likely become depleted at later evolutionary stages.