A fitting program for molecules with two inequivalent methyl tops and a plane of symmetry at equilibrium: Application to new microwave and millimeter-wave measurements of methyl acetate

Tudorie, M.; Kleiner, Isabelle; Hougen, Jon J.T.; Melandri, Sonia; Sutikdja, Lilian L.W.; Stahl, Wolfgang

doi:10.1016/j.jms.2011.07.005

Cited by 61 publications

(117 citation statements)

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“…As explained in (Tudorie et al 2011), terms in this Hamiltonian can be constructed by taking symmetry-allowed and Hermitian products of a rotational factor (chosen from operators of the form J The BELGI-C s -2Tops program has been applied for fitting high resolution torsion-rotational spectra of molecules with: (i) two nonequivalent methyl rotors; (ii) two different three-fold barriers and (iii) a plane of symmetry at equilibrium, e.g. methyl acetate (Tudorie et al 2011), methyl propionate (Nguyen et al 2012), three isomers of dimethyl benzaldehyde (Tudorie et al 2013) and ethyl methyl ketone (Nguyen et al 2014). In the case of DMS, we modified the code slightly so that all internal rotor parameters corresponding to one methyl group, referred as top 1, possess the same magnitudes as those of the other methyl top, referred as top 2.…”

Section: Theoretical Modelsmentioning

confidence: 99%

“…The second code is a slightly modified version of the BELGI-C s -2Tops code, which has been applied so far for molecules with two nonequivalent internal rotors (Tudorie et al 2011). One of the differences with XIAM is the choice of the axis system.…”

Section: Theoretical Modelsmentioning

confidence: 99%

“…One of the differences with XIAM is the choice of the axis system. The BELGI-C s -2Tops code uses the so-called "quasi principalaxis-method" (Tudorie et al 2011), instead of the rho axis method (Hougen et al 1994), which requires placing the z axis nearly parallel to the top axis. The quasi PAM takes its name from the fact that the coefficients of the three quadratic rotational operators (J x J y +J y J x ), (J y J z +J z J y ) and (J z J x +J x J z ) are kept fixed to zero in the fits.…”

Section: Theoretical Modelsmentioning

confidence: 99%

“…In the first diagonalization step, only the lowest order, pure torsional operators of the Hamiltonian are considered (Eq. (3) of Tudorie et al (2011) and Eq. (6) of Ohashi et al (2004)).…”

Section: Theoretical Modelsmentioning

confidence: 99%

“…In the present calculation, we set ktronc = 10 as in the case of methyl acetate (Tudorie et al 2011), e.g. 441 torsional basis functions are used in this first step.…”

Section: Theoretical Modelsmentioning

confidence: 99%

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Laboratory microwave, millimeter wave and far-infrared spectra of dimethyl sulfide

Jabri

Van

Nguyen

et al. 2016

A&A

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Context. Dimethyl sulfide, CH 3 SCH 3 (DMS), is a nonrigid, sulfur-containing molecule whose astronomical detection is considered to be possible in the interstellar medium. Very accurate spectroscopic constants were obtained by a laboratory analysis of rotational microwave and millimeter wave spectra, as well as rotation-torsional far-infrared (FIR) spectra, which can be used to predict transition frequencies for a detection in interstellar sources. Aims. This work aims at the experimental study and theoretical analysis of the ground torsional state and ground torsional band ν 15 of DMS in a large spectral range for astrophysical use. Methods. The microwave spectrum was measured in the frequency range 2−40 GHz using two Molecular Beam Fourier Transform MicroWave (MB-FTMW) spectrometers in Aachen, Germany. The millimeter spectrum was recorded in the 50−110 GHz range. The FIR spectrum was measured for the first time at high resolution using the FT spectrometer and the newly built cryogenic cell at the French synchrotron SOLEIL. Results. DMS has two equivalent methyl internal rotors with a barrier height of about 730 cm −1 . We performed a fit, using the XIAM and BELGI-C s -2Tops codes, that contained the new measurements and previous transitions reported in the literature for the ground torsional state ν t = 0 (including the four torsional species AA, AE, EA and EE) and for the ground torsional band ν 15 = 1 ← 0 (including only the AA species). In the microwave region, we analyzed 584 transitions with J ≤ 30 of the ground torsional state ν t = 0 and 18 transitions with J ≤ 5 of the first excited torsional state ν t = 1. In the FIR range, 578 transitions belonging to the torsional band ν 15 = 1 ← 0 with J ≤ 27 were assigned. Totally, 1180 transitions were included in a global fit with 21 accurately determined parameters. These parameters can be used to produce a reliable line-list for an astrophysical detection of DMS.

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Section: Theoretical Modelsmentioning

confidence: 99%

Section: Theoretical Modelsmentioning

confidence: 99%

Section: Theoretical Modelsmentioning

confidence: 99%

“…In the first diagonalization step, only the lowest order, pure torsional operators of the Hamiltonian are considered (Eq. (3) of Tudorie et al (2011) and Eq. (6) of Ohashi et al (2004)).…”

Section: Theoretical Modelsmentioning

confidence: 99%

“…In the present calculation, we set ktronc = 10 as in the case of methyl acetate (Tudorie et al 2011), e.g. 441 torsional basis functions are used in this first step.…”

Section: Theoretical Modelsmentioning

confidence: 99%

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Laboratory microwave, millimeter wave and far-infrared spectra of dimethyl sulfide

Jabri

Van

Nguyen

et al. 2016

A&A

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Molecular Spectroscopy

Giesen

Rice

Maier

et al. 2014

Laboratory Astrochemistry

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Conformational Analysis of Green Apple Flavour: The Gas‐Phase Structure of Ethyl Valerate Validated by Microwave Spectroscopy

Mouhib

Stahl

2012

ChemPhysChem

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We report on the microwave spectrum of ethyl valerate, C(4)H(9)-COO-C(2)H(5), observed by molecular beam Fourier transform microwave spectroscopy (MB-FTMW). Highly accurate rotational and centrifugal distortion constants of the two most abundant conformers were determined. Their structure was investigated by comparison of the experimental rotational constants with those obtained by quantum chemical calculations. MP2/ 6-311++G(d,p) calculations failed to give a proper description of the observed conformers in the supersonic jet. Therefore, also other basis sets were tried using Hartree-Fock, second-order Møller-Plesset (MP2), and B3LYP methods to predict the observed gas-phase structures of the molecule. The quantum chemical results guided the conformer assignment of the rotational constants, obtained from the microwave experiment. One of the two observed conformers has C(s) symmetry, while the most abundant conformer has C(1) symmetry. The main conformer possesses a strong spectrum with high intensities. Additionally, harmonic frequency calculations at different levels of theory where carried out and a low lying vibration of the entire n-butyl group against the rest of the molecule was identified. The symbiotic interplay of microwave gas-phase investigations and quantum chemical calculations becomes evident in our results.

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A fitting program for molecules with two inequivalent methyl tops and a plane of symmetry at equilibrium: Application to new microwave and millimeter-wave measurements of methyl acetate

Cited by 61 publications

References 25 publications

Laboratory microwave, millimeter wave and far-infrared spectra of dimethyl sulfide

Laboratory microwave, millimeter wave and far-infrared spectra of dimethyl sulfide

Molecular Spectroscopy

Conformational Analysis of Green Apple Flavour: The Gas‐Phase Structure of Ethyl Valerate Validated by Microwave Spectroscopy

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