The Third and Fourth Torsional States of Acetaldehyde

Kleiner, Isabelle; Hougen, Jon T.; Grabow, Jens‐Uwe; Belov, S. P.; Tretyakov, M.Yu.; Cosléou, J.

doi:10.1006/jmsp.1996.0182

Cited by 79 publications

(82 citation statements)

References 6 publications

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“…The principal advantage of the RAM general approach used in our code BELGI, which is publicly available 1 , is its general approach that simultaneously takes into account the A-and E-symmetry states in our fit. All the torsional levels up to a truncation limit of v t = 8 are carefully tested and the interactions within the rotation-torsion energy levels are also included in the rotation-torsion Hamiltonian matrix elements (Kleiner et al 1996). The various rotational, torsional, and coupling terms between rotation and torsion that we used for the fit of the HCOO 13 CH 3 species were defined previously for the normal methyl formate species (Carvajal et al 2007).…”

Section: Assignments and Fit Of The Hcoo 13 Ch 3 Spectrummentioning

confidence: 99%

THz spectroscopy and first ISM detection of excited torsional states of¹³C-methyl formate

Haykal¹,

Carvajal²,

Tercero³

et al. 2014

A&A

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Context. An astronomical survey of interstellar molecular clouds needs a previous analysis of the spectra in the microwave and sub-mm energy range of organic molecules to be able to identify them. We obtained very accurate spectroscopic constants in a comprehensive laboratory analysis of rotational spectra. These constants can be used to predict the transitions frequencies very precisely that were not measured in the laboratory. Aims. We present the experimental study and its theoretical analysis for two 13 C-methyl formate isotopologues to detect these two isotopologues for the first time in their excited torsional states, which lie at 130 cm −1 (200 K) in Orion-KL. Methods. New spectra of HCOO 13 CH 3 ( 13 C 2 ) methyl formate were recorded with the mm-and submm-wave spectrometer in Lille from 50 to 940 GHz. A global fit for v t = 0 and 1 was accomplished with the BELGI program to reproduce the experimental spectra with greater accuracy. Results. We analysed 5728 and 2881 new lines for v t = 0 and 1 for HCOO 13 CH 3 . These new lines were globally fitted with 846 previously published lines for v t = 0. In consequence, 52 parameters of the RAM Hamiltonian were accurately determined and the value of the barrier height (V 3 = 369.93168(395) cm −1 ) was improved. We report the detection of the first excited torsional states (v t = 1) in Orion-KL for the 13 C 2 and 13 C 1 methyl formate based on the present analysis and previously published data. We provide column densities, isotopic abundances, and vibrational temperatures for these species. Conclusions. Following this work, accurate prediction can be provided. This permits detecting 135 features of the first excited torsional states of 13 C-methyl formate isotopologues in Orion-KL in the 80−280 GHz frequency range, without missing lines.

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Section: Assignments and Fit Of The Hcoo 13 Ch 3 Spectrummentioning

confidence: 99%

THz spectroscopy and first ISM detection of excited torsional states of¹³C-methyl formate

Haykal¹,

Carvajal²,

Tercero³

et al. 2014

A&A

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“…It was therefore suggested by Lees [22] to refer to E1 and E2 levels as E levels where the sign of K distinguishes the two symmetries. The eigenvalues of the torsional Hamiltonian for methanol [23], acetaldehyde [24], and acetic acid [25] are depicted in Fig. 2 [16] for the A, E1, and E2 torsional states, respectively.…”

Section: Torsionmentioning

confidence: 99%

“…We have calculated the sensitivity coefficients of many (>1000) transitions in methanol, acetaldehyde, acetamide, methyl formate, and acetic acid, using the constants listed in Refs. [23][24][25]29,30], respectively. In Table II sensitivity coefficients of selected transitions in the vibrational ground state (ν t = 0) of these molecules are listed.…”

Section: Scaling and Sensitivity Coefficientsmentioning

confidence: 99%

Sensitivity of transitions in internal rotor molecules to a possible variation of the proton-to-electron mass ratio

Jansen

Kleiner

et al. 2011

Phys. Rev. A

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Recently, methanol was identified as a sensitive target system to probe variations of the proton-to-electron mass ratio μ [Jansen et al., Phys. Rev. Lett. 106, 100801 (2011)]. The high sensitivity of methanol originates from the interplay between overall rotation and hindered internal rotation of the molecule; that is, transitions that convert internal rotation energy into overall rotation energy, or vice versa, have an enhanced sensitivity coefficient, K μ . As internal rotation is a common phenomenon in polyatomic molecules, it is likely that other molecules display similar or even larger effects. In this paper we generalize the concepts that form the foundation of the high sensitivity in methanol and use this to construct an approximate model which makes it possible to estimate the sensitivities of transitions in internal rotor molecules with C 3v symmetry, without performing a full calculation of energy levels. We find that a reliable estimate of transition sensitivities can be obtained from the three rotational constants (A, B, and C) and three torsional constants (F , V 3 , and ρ). This model is verified by comparing obtained sensitivities for methanol, acetaldehyde, acetamide, methyl formate, and acetic acid with a full analysis of the molecular Hamiltonian. Of the molecules considered, methanol is by far the most suitable candidate for laboratory and cosmological tests searching for a possible variation of μ.

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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%

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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The Third and Fourth Torsional States of Acetaldehyde

Cited by 79 publications

References 6 publications

THz spectroscopy and first ISM detection of excited torsional states of¹³C-methyl formate

THz spectroscopy and first ISM detection of excited torsional states of¹³C-methyl formate

Sensitivity of transitions in internal rotor molecules to a possible variation of the proton-to-electron mass ratio

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

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The Third and Fourth Torsional States of Acetaldehyde

Cited by 79 publications

References 6 publications

THz spectroscopy and first ISM detection of excited torsional states of13C-methyl formate

THz spectroscopy and first ISM detection of excited torsional states of13C-methyl formate

Sensitivity of transitions in internal rotor molecules to a possible variation of the proton-to-electron mass ratio

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

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THz spectroscopy and first ISM detection of excited torsional states of¹³C-methyl formate

THz spectroscopy and first ISM detection of excited torsional states of¹³C-methyl formate

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