A new joint analysis of the ground and first excited torsional states of methylformate

Ilyushin, V. V.; Kryvda, A.V.; Alekseev, E. A.

doi:10.1016/j.jms.2009.01.016

Cited by 71 publications

(104 citation statements)

References 28 publications

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“…(8) (1) Observed transitions with E upper < ∼ 650 K. (2) Reference number of the corresponding data set (see Table 1 Ilyushin et al (2009). For the transitions coming from the JPL database, the line strength is calculated from the formulae of Pickett et al (1998).…”

Section: Discussionmentioning

confidence: 99%

HCOOCH₃as a probe of temperature and structure in Orion-KL

Favre

Despois

Brouillet

et al. 2011

A&A

238

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Context. The Orion Kleinmann-Low nebula (Orion-KL) is a complex region of star formation. Whereas its proximity allows studies on a scale of a few hundred AU, spectral confusion makes it difficult to identify molecules with low abundances. Aims. We studied an important oxygenated molecule, HCOOCH 3 , to characterize the physical conditions, temperature, and density of the different molecular source components. Methyl formate presents strong close rotational transitions covering a wide range of energy, and its emission in Orion-KL is not contaminated by the emission of N-bearing molecules. This study will help in the future 1) to constrain chemical models for the formation of methyl formate in gas phase or on grain mantles and 2) to search for more complex or prebiotic molecules. Methods. We used high-resolution observations from the IRAM Plateau de Bure Interferometer to reduce spectral confusion and to better isolate the molecular emission regions. We used twelve data sets with a spatial resolution down to 1.8 × 0.8 . Continuum emission was subtracted by selecting apparently line-free channels. Results. We identify 28 methyl formate emission peaks throughout the 50 field of observations. The two strongest peaks, named MF1 and MF2, are in the Compact Ridge and in the southwest of the Hot Core, respectively. From a comparison with single-dish observations, we estimate that we miss less than 15% of the flux and that spectral confusion is still prevailing as half of the expected transitions are blended over the region. Assuming that the transitions are thermalized, we derive the temperature at the five main emission peaks. At the MF1 position in the Compact Ridge we find a temperature of 80 K in a 1.8 × 0.8 beam size and 120 K on a larger scale (3.6 × 2.2 ), suggesting an external source of heating, whereas the temperature is about 130 K at the MF2 position on both scales. Transitions of methyl formate in its first torsionally excited state are detected as well, and the good agreement of the positions on the rotational diagrams between the ground state and the v t = 1 transitions suggests a similar temperature. The LSR velocity of the gas is between 7.5 and 8.0 km s −1 depending on the positions and column density peaks vary from 1.6 × 10 16 to 1.6 × 10 17 cm −2 . A second velocity component is observed around 9−10 km s −1 in a north-south structure stretching from the Compact Ridge up to the BN object, and this component is warmer at the MF1 peak. The two other C 2 H 4 O 2 isomers are not detected, and the derived upper limit for the column density is ≤3 × 10 14 cm −2 for glycolaldehyde and ≤2 × 10 15 cm −2 for acetic acid. From the 223 GHz continuum map, we identify several dust clumps with associated gas masses in the range 0.8 to 5.8 M . Assuming that the methyl formate is spatially distributed as the dust is, we find relative abundances of methyl formate in the range ≤0.1 × 10 −8 to 5.2 × 10 −8 . We suggest a relation between the methyl formate distribution and shocks as traced by 2.12 μm H 2 emission.

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Section: Discussionmentioning

confidence: 99%

HCOOCH₃as a probe of temperature and structure in Orion-KL

Favre

Despois

Brouillet

et al. 2011

A&A

238

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“…Some previously measured lines for the normal species of methyl formate also showed discrepancies (Carvajal et al 2007) and needed to be remeasured using a higher precision instrument. During the course of the present paper remeasurements, as well as new measurements, were underway for H 12 COO 12 CH 3 normal methyl formate and a data set containing about 10 000 lines has been included in a global fit using the RAM method (Ilyushin et al 2009). …”

Section: Discussionmentioning

confidence: 99%

“…Complementary to the ErHam approach that fits all torsional states separately (and hence gets as many set of parameters as torsional states, but also avoids the problems of having errors spread out among the various torsional states), the RAM approach can be used to fit all available data simultaneously corresponding to the torsional bath levels (v t = 0, 1, and 2), not only for the normal species (Ilyushin et al 2009), but also for the 13 C 1 -methyl formate H 13 COOCH 3 isotopologue, for which such data have been published very recently. In addition to decreasing the number of fitted parameters in the global model relative to a separate fit of torsional levels, the RAM method presents the advantage of including terms corresponding to rotation-torsion interactions between different torsional states in the Hamiltonian matrix.…”

Section: Discussionmentioning

confidence: 99%

Rotational spectrum of¹³C₂-methyl formate (HCOO¹³CH₃) and detection of the two¹³C-methyl formate in Orion

Carvajal¹,

Margulès

Tercero

et al. 2009

A&A

116

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Context. Laboratory measurements and analysis of the microwave and millimeter-wave spectra of potential interstellar molecules are a prerequisite for their subsequent identification by radioastronomical techniques. The spectral analysis provides spectroscopic parameters that are used in the assignment procedure of the laboratory spectra, and that also predict the frequencies of transitions not measured in the laboratory with a high degree of precision.Aims. An experimental laboratory study and its theoretical analysis is presented for 13 C 2 -methyl formate (HCOO 13 CH 3 ) allowing a search for this isotopologue in the Orion molecular cloud. The 13 C 1 -methyl formate (H 13 COOCH 3 ) molecule was also searched for in this interstellar cloud, using previously published spectroscopic data. Methods. The experimental spectra of 13 C 2 -methyl formate were recorded in the microwave and sub-mm energy ranges (4-20 GHz, 8-80 GHz, 150-700 GHz). The spectra were analyzed using the Rho-Axis Method (RAM), which takes the CH 3 internal rotation and the coupling between internal rotation and global rotation into account. Results. Twenty-seven spectroscopic constants of 13 C 2 -methyl formate have been obtained from a fit of 936 transitions of the ground torsional state with a standard (unitless) deviation of 1.08. A prediction of line positions and intensities is also produced. This prediction allowed us to identify 230 13 C 2 -methyl formate lines in the Orion interstellar molecular cloud. We refitted all previously published ground state transitions of the 13 C 1 -methyl formate molecule in order to provide a prediction of its ground state spectrum. 234 lines of 13 C 1 -methyl formate were detected in the Orion interstellar cloud using that prediction.

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“…This formalism and the corresponding software (the BELGICs code) have been applied with success to a number of internal rotor molecules observed in the ISM, such as acetaldehyde CH 3 CHO (Kleiner et al 1996a), acetamide CH 3 CONH 2 (Hollis et al 2006), acetic acid CH 3 COOH (Ilyushin et al 2008(Ilyushin et al , 2013, and different isotopologs of methyl formate (Carvajal et al 2007(Carvajal et al , 2009(Carvajal et al , 2010Ilyushin et al 2009;Margulès et al 2010;Tercero et al 2012;Haykal et al 2014). The BELGI code used in this study is available on the web 1 .…”

Section: Theoretical Modelmentioning

confidence: 99%

“…Since its discovery in Sgr B2 (Brown et al 1975;Churchwell et al 1975), extensive spectroscopic studies have been carried out for the main species (Bauder 1979;Demaison et al 1983;Plummer et al 1984Plummer et al , 1986Oesterling et al 1999;Karakawa et al 2001;Ogata et al 2004;Carvajal et al 2007;Maeda et al 2008b;Ilyushin et al 2009;Full Tudorie et al 2012;Kobayashi et al 2013) and for its isotopologs (Curl 1959;Oesterling et al 1995;Willaert et al 2006;Maeda et al 2008a,b;Margulès et al 2009Margulès et al , 2010Carvajal et al 2009Carvajal et al , 2010Coudert et al 2012Coudert et al , 2013Tercero et al 2012;Haykal et al 2014). This spectroscopic database for the methyl formate molecule has given rise to an increasing identification of the spectral lines in different interstellar surveys.…”

Section: Introductionmentioning

confidence: 99%

THz extended spectrum of the monodeuterated methyl formate (DCOOCH₃)

Duan

Carvajal

et al. 2015

A&A

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Context. Laboratory spectral recordings and an accurate molecular spectral analysis of any potential interstellar molecule are essential for generating a complete spectroscopic line list. This permits predicting the frequencies and intensities of any transition so that subsequently, it can be identified in the interstellar medium. Aims. Our analysis of DCOOCH 3 aims to provide a comprehensive spectral catalog that encompasses as much as possible the frequency coverage of the new-generation far-IR and submillimeter wave observation facilities. Methods. We newly measured the rotational spectrum of DCOOCH 3 in the laboratory of the Jet Propulsion Laboratory in the frequency range of 0.85 to 1.5 THz. We jointly analyzed the new data with literature data using the rho axis method, which is a tool developed for the spectral analysis of molecules with large-amplitude internal CH 3 rotors. Results. We fit 27 spectroscopic constants of DCOOCH 3 to 3763 transitions with highest values of J = 69 and K a = 36 of the ground torsional state with a standard (unitless) deviation of 0.97. With respect to previous work, this is a significantly better result that was obtained with 2060 more transitions, and we also achieved a better accuracy for the new parameter values.

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A new joint analysis of the ground and first excited torsional states of methylformate

Cited by 71 publications

References 28 publications

HCOOCH₃as a probe of temperature and structure in Orion-KL

HCOOCH₃as a probe of temperature and structure in Orion-KL

Rotational spectrum of¹³C₂-methyl formate (HCOO¹³CH₃) and detection of the two¹³C-methyl formate in Orion

THz extended spectrum of the monodeuterated methyl formate (DCOOCH₃)

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A new joint analysis of the ground and first excited torsional states of methylformate

Cited by 71 publications

References 28 publications

HCOOCH3as a probe of temperature and structure in Orion-KL

HCOOCH3as a probe of temperature and structure in Orion-KL

Rotational spectrum of13C2-methyl formate (HCOO13CH3) and detection of the two13C-methyl formate in Orion

THz extended spectrum of the monodeuterated methyl formate (DCOOCH3)

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Product

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HCOOCH₃as a probe of temperature and structure in Orion-KL

HCOOCH₃as a probe of temperature and structure in Orion-KL

Rotational spectrum of¹³C₂-methyl formate (HCOO¹³CH₃) and detection of the two¹³C-methyl formate in Orion

THz extended spectrum of the monodeuterated methyl formate (DCOOCH₃)