Reinvestigation of the ground and first torsional state of methylformate

Carvajal, M.; Willaert, F.; Demaison, J.; Kleiner, Isabelle

doi:10.1016/j.jms.2007.08.009

Cited by 41 publications

(106 citation statements)

References 25 publications

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“…(up a truncation limit of v t = 8 carefully tested) and the interactions within those torsion-rotation energy levels are also included in the rotationtorsion Hamiltonian matrix elements (Kleiner et al 1996b). The various terms we are using in the Hamiltonian for the fit of the 13 C 2 -(and also for 13 C 1 )-methyl formate species, rotational terms, internal rotation terms, and the coupling between internal rotation and global rotation have been described before for normal methyl formate (Carvajal et al 2007). …”

Section: Theoretical Modelmentioning

confidence: 99%

“…It is, however, clear that some blended lines show observed-calculated values with high residuals. Table 2 shows the values for the 28 rotation-torsion parameters (including one fixed parameter, F) used in our final fit for HCOO 13 CH 3 , together with the values for the 49 parameters needed in the fit of the normal species H 12 COO 12 CH 3 (Carvajal et al 2007). Even though the data set is very different and is much more extended for the normal species (3496 lines belonging to the ground torsional state v t = 0 fitted with a standard deviation of 94 kHz and 774 lines belonging to the first excited state v t = 1 fitted with a standard deviation of 84 kHz), one can see that the low-order parameters (n = 2) agree within 5%, except for V 3 which is discussed below.…”

Section: Assignments and Fitmentioning

confidence: 99%

“…For the normal species of methyl formate and for 13 C 2 -methyl formate we show the values of those parameters obtained from our global fits, after transforming the RAM rotational constants into the PAM constants (following a procedure described in Carvajal et al 2007). The angle θ RAM between the RAM axis system and the PAM axis system varies from the normal species (24.83 • ) to 13 C 2 -methyl formate (23.68 • ) by 4.6%.…”

Section: Assignments and Fitmentioning

confidence: 99%

“…Chronologically the measurements carried out for the ground torsional state (v t = 0) were performed in the spectral range 8-58 GHz (Bauder 1979), 150-313 GHz (Demaison et al 1983), 216-506 GHz (Plummer et al 1984), 200-352 GHz (Plummer et al 1986), 250-510 GHz (Oesterling et al 1999), 7-200 GHz (Karakawa et al 2001), 567-669 GHz (Carvajal et al 2007), and 110-380 GHz (Maeda et al 2008a). In 2003 and 2004, a number of transitions were analyzed for the first time in the first excited torsional state v t = 1 (Odashima et al 2003;Ogata et al 2004).…”

Section: Introductionmentioning

confidence: 99%

“…In 2007, 4270 transition lines covering the spectral range up to 669 GHz (with J max = 62, K max = 22 for v t = 0; and J max = 18, K max = 7 for v t = 1) were globally analyzed using the RAM or Rho-Axis Method (Lin & Swalen 1959;Herbst et al 1984;Hougen et al 1994). This global fit of the A-and E-species required 49 parameters to achieve root-mean-square deviations of 94 kHz and 84 kHz corresponding to 3486 and 774 transitions in the ground and first excited torsional states, respectively (Carvajal et al 2007). The number of lines measured in the ground torsional state v t = 0 of normal methyl formate has increased very recently by measurements performed using the Fast Scan Submillimeter Spectroscopic Technique (FASSST) and 5366 lines in v t = 0 were fitted up to 510 GHz (Maeda et al 2008a).…”

Section: Introductionmentioning

confidence: 99%

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

Carvajal¹,

Margulès

Tercero

et al. 2009

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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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Section: Theoretical Modelmentioning

confidence: 99%

Section: Assignments and Fitmentioning

confidence: 99%

Section: Assignments and Fitmentioning

confidence: 99%