Ha Vinh Lam Nguyen

Ha Vinh Lam Nguyen
Interuniversity Laboratory of Atmospheric Systems | LISA · Université Paris-Est Créteil

Dr.

About

117
Publications
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Introduction
Lam Nguyen currently works at the Université Paris-Est Créteil, Interuniversity Laboratory of Atmospheric Systems. Lam does research in Spectroscopy and Physical Chemistry. The current project is 'Microwave spectroscopy on molecules with large amplitude motions'.

Publications

Publications (117)
Article
Large amplitude motions (LAMs) form a fundamental phenomenon that demands the development of specific theoretical and Hamiltonian models. In recent years, along with the strong progress in instrumental techniques on high-resolution microwave spectroscopy and computational capacity in quantum chemistry, studies on LAMs have become very diverse. Larg...
Article
Full-text available
The rotational spectrum of phenyl acetate, CH3COOC6H5, is measured using a free jet absorption millimeter-wave spectrometer in the range from 60 to 78 GHz and two pulsed jet Fourier transform microwave spectrometers covering a total frequency range from 2 to 26.5 GHz. The features of two large amplitude motions, the methyl group internal rotation a...
Article
Full-text available
The gas-phase structures of the fruit ester methyl hexanoate, CH3-O-(C=O)-C5H11, have been determined using a combination of molecular jet Fourier-transform microwave spectroscopy and quantum chemistry. The microwave spectrum was measured in the frequency range of 3 to 23 GHz. Two conformers were assigned, one with Cs symmetry and the other with C1...
Article
The pure rotational spectrum of the open shell difluorocyanomethyl radical, ĊF2CN, has been measured using two Balle-Flygare-type cavity Fourier-Transform-Microwave (FTMW) spectrometers both equipped with pulsed discharged nozzles. A total of 156 transitions (from N = 1 – 0 to 6 – 5, and Ka = 0, 1, 2, 3) in the electronic ground state were observed...
Article
A simple method to determine unperturbed rotational constants in the presence of internal rotation is proposed and applied on the microwave data sets of 2-acetylfuran and 2-acetylthiophene, featuring intermediate barriers to methyl internal rotation of about 300 cm⁻¹. Two general approaches, global fits of all torsional species simultaneously and l...
Article
The microwave spectra of thiophene and 2-acetylthiophene were recorded in the frequency range from 2 to 40 GHz using two molecular jet Fourier transform microwave spectrometers. For 2-acetylthiophene, two conformers with a syn and an anti orientation of the S1-C2 and C6O bonds (with respect to the C2-C6 bond) were identified, and the syn-conformer...
Article
In the rotational spectroscopy community, several popular codes are available to treat multiple internal rotors in a molecule. In terms of the pros and the cons of each code, it often is a difficult task to decide which program to apply to a specific internal rotation problem. We faced this issue when dealing with the spectroscopic fingerprint of 4...
Article
The microwave spectrum of 2‐acetyl‐3‐methylthiophene (2A3MT) was recorded in the frequency range from 2 to 26.5 GHz using a molecular jet Fourier transform microwave spectrometer and could be fully assigned to the anti‐conformer of the molecule, while the syn‐conformer was not observable. Torsional splittings of all rotational transitions in form o...
Article
Using a molecular jet Fourier transform spectrometer, the microwave spectrum of E-3-penten-2-one, also called methyl propenyl ketone, was recorded in a range from 2.0 to 26.5 GHz. Two conformers, antiperiplanar (ap) and synperiplanar (sp), could be identified. Complicated splitting patterns arising due to the internal rotation of the acetyl methyl...
Article
The rotational spectrum of 2-fluoro-4-chlorotoluene was studied in the frequency range 4 to 24 GHz by Fourier transform microwave spectroscopy. Fine torsional splitting into doublets was observed for all rotational transitions due to methyl group internal rotation hindering with a barrier height of about 230 cm⁻¹. In combination with the quadrupole...
Article
Full-text available
Inversion tunneling in a symmetric double minimum potential is a challenging large amplitude motion problem which causes all rotational energy levels to split into a symmetric and an antisymmetric level. Not like other types of large amplitude motion such as internal rotation, inversion tunneling appears much rarer, but the fundamental knowledge ga...
Article
The microwave spectrum of 2,5-dimethylpyrrole was recorded using a molecular jet Fourier transform microwave spectrometer operating in the frequency range from 2 to 26.5 GHz. Only one stable conformer was observed as expected and confirmed by quantum chemical calculations carried out to complement the experimental analysis. The two equivalent methy...
Article
2-Chloro-4-fluorotoluene was investigated using a combination of molecular jet Fourier transform microwave spectroscopy in the frequency range from 5 to 21 GHz and quantum chemistry. The molecule experiences an internal rotation of the methyl group, which causes fine splittings of all rotational transitions into doublets with separation on the orde...
Article
The microwave spectrum of 3,4-dimethylfluorobenzene was measured using a pulsed molecular jet Fourier transform microwave spectrometer operating in the frequency range from 2.0 to 26.5 GHz with the goal of quantifying the steric effects on the barriers to internal rotation of the two inequivalent methyl groups. Due to these torsional motions, split...
Article
The microwave spectrum of the fruit ester methyl valerate was recorded using two molecular jet Fourier transform spectrometers covering the frequency range from 2 to 40 GHz. Quantum chemical calculations yielded 11 minima for the anti ester configuration, among them two were identified in the experimental spectrum. The methyl group in the methoxy m...
Article
The spectra of N-ethyl methyl amine, CH3(NH)CH2CH3, were measured using a molecular jet Fourier transform microwave spectrometer in the frequency range of 2 GHz–26.5 GHz. Splittings due to proton inversion tunneling, Coriolis coupling, ¹⁴N quadrupole coupling, and methyl internal rotation were fully resolved. The experimentally deduced rotational c...
Article
A large variety of molecules contain large amplitude motions (LAMs), inter alia internal rotation and inversion tunneling, resulting in tunneling splittings in their rotational spectrum. We will present the modern strategy to study LAMs using a combination of molecular jet Fourier transform microwave spectroscopy, spectral modeling, and quantum che...
Article
Rotational transitions of gauche-acetone cyanohydrin are measured in the microwave range between 5 and 23 GHz. Results from quantum chemical calculations indicate that the hydrogen atom of the hydroxyl group undergoes a tunneling motion connecting two equivalent structures. The observed signals are assigned to the two lowest tunneling substates 0+...
Article
The long-standing ambiguity of the molecular planarity when an alkyl group is attached on a system with conjugated double bonds is a great challenge for both experiments and theory. This also holds for the case of 2-propionylthiophene (2PT) where a propionyl group is attached at the second position of the planar, aromatic thiophene ring. Results fr...
Article
The molecular structure of 3-methylpyrrole in the gas phase has been determined using a combination of high-resolution spectroscopy and quantum chemical calculations. The rotational spectrum was recorded using a molecular jet Fourier transform microwave spectrometer covering the frequency range from 2.0 to 26.5 GHz. The experimental data were analy...
Article
The microwave spectrum of methyl n-propyl sulfide, CH3-S-CH2-CH2-CH3, was recorded in the frequency region from 2.0 to 26.5 GHz, revealing three conformers. Quantum chemical calculations were carried out to support the experimental work. Fine splittings arising from the internal rotation of the methyl group attached to the sulfur atom were resolved...
Article
Methyl n ‐alkyl ketones form a class of molecules with interesting internal dynamics in the gas‐phase. They contain two methyl groups undergoing internal rotations, the acetyl methyl group and the methyl group at the end of the alkyl chain. The torsional barrier of the acetyl methyl group is of special importance, since it allows for the discrimina...
Article
The microwave rotational spectra of 3-fluorotoluene and its seven ¹³C isotopic species have been recorded at natural abundance in the frequency range from 4 to 26 GHz using a pulsed molecular jet Fourier transform microwave spectrometer. The molecular structure comprising bond lengths and angles as well as parameters describing the methyl torsion w...
Article
Full-text available
The Cover Feature shows the structure of coumarin, a natural substance with the specific scent of maibowle. The microwave‐determined bond lengths and bond angles reflect pertubations of the π electron delocalization in coumarin. The large, negative inertial defect indicates pronounced out‐of‐plane motions of the ring. More information can be found...
Article
Large amplitude motion of methyl groups in isolated molecules is a fundamental phenomenon in molecular physics. The methyl torsional barrier is sensitive to the steric and electronic environment in the surrounding of the methyl group, making the methyl group a detector of the molecular structure. To probe this effect, the microwave spectrum of 2,6‐d...
Article
The molecular jet Fourier-transform microwave spectrum of 4,5-dimethylthiazole has been recorded between 2.0 and 26.5 GHz, revealing torsional splittings arising from two inequivalent methyl internal rotations with relatively low hindering barriers and nitrogen quadrupole hyperfine structures. Two global fits with 1009 hyperfine components of 97 ro...
Article
The microwave spectra of the natural substance coumarin, a planar aromatic molecule with the specific scent of maibowle, a popular fruit punch served in spring and early summer, were recorded using a molecular jet Fourier transform microwave spectrometer working in the frequency range from 4.0 to 26.5 GHz. The rotational constants and centrifugal d...
Article
The rotational spectrum of 2-methylthiazole was recorded using two pulsed molecular jet Fourier transform microwave spectrometers operating in the frequency range of 2–40 GHz. Due to the internal rotation of the methyl group, all rotational transitions were split into A and E symmetry species lines, which were analyzed using the programs XIAM and B...
Article
The XIAM code is one of the most frequently used programs to treat the microwave spectra of molecules with up to three methyl internal rotors. XIAM is user-friendly and fast, but often shows difficulties in dealing with low torsional barriers. An example is the case of m-methylanisole where the methyl group attached at the meta-position of the ring...
Article
The Fourier transform microwave spectrum of 4-methylacetophenone recorded from 8 GHz to 18 GHz under jet-cooled conditions has revealed large tunneling splittings arising from a low barrier to internal rotation of the ring methyl group and small splittings from a high torsional barrier of the acetyl methyl group. The large splittings are especially...
Article
We report on the structures of two conformers of 2-thiophenecarboxaldehyde as obtained using a combination of molecular jet Fourier-transform microwave spectroscopy and quantum chemical calculations. The microwave spectrum was recorded using two spectrometers operating in the frequency ranges of 2.0 to 26.5 GHz and 26.5 to 40.0 GHz. The spectra of...
Article
The substitution rs and semi-experimental equilibrium reSE structures of the two conformers of 2-ethylfuran were obtained using a combination of microwave spectroscopy and quantum chemistry. The microwave spectrum was recorded using a molecular jet Fourier-transform spectrometer operating in the frequency range of 2.0 GHz–26.5 GHz. The spectra of a...
Article
The microwave spectrum of heptan-2-one (CH3COC4H8CH3) was recorded in the frequency range from 2 to 40 GHz using two molecular jet Fourier transform microwave spectrometers. The two energetically most favorable conformers could be identified and fitted with standard deviations close to measurement accuracy. The splittings arising from the internal...
Article
The rotational spectra of coffee furanone (2-methyltetrahydrofuran-3-one) have been measured in the frequency range from 2.0 to 26.5 GHz using a molecular jet Fourier transform microwave spectrometer. Quantum chemical calculations used for the conformational analysis yielded two stable twist conformers, which were described using the Cremer–Pople n...
Article
Using two molecular jet Fourier transform microwave spectrometers, the rotational spectrum of 2-methylpyrrole was recorded in the frequency range from 2 to 40 GHz. From the torsional splittings due to the internal rotation of the methyl group a barrier height of 279.7183(26) cm⁻¹ was deduced. Because of the ¹⁴N nucleus, all lines show a quadrupole...
Article
Low barriers to internal rotations are especially challenging for both the experimental and theoretical determinations because they result in large tunneling splittings which are hard to assign and in potential functions that can be difficult to model. In the present work, the internal rotations of two methyl groups of 2,4-dimethylanisole were anal...
Poster
Full-text available
The torsional barriers of methyl groups attached to aromatic compounds are hard to predict. In addition, studying the 14N quadrupole hyperfine structure gives us infor- mation on the electric field gradient at the site of the 14N nucleus and consequently on the nature of its chemical bonds. All these reasons motivated us to investigate two methyl d...
Article
The Cover Feature shows how the conformational structures of hexan‐2‐one could be linked to the internal rotation of its acetyl methyl group. This allows the creation of a general rule to predict the torsional barriers in methyl alkyl ketones. More information can be found in the Article by M. Andresen et al.
Article
Using two molecular jet Fourier transform spectrometers, the microwave spectrum of hexan‐2‐one, also called methyl n‐butyl ketone, was recorded in the frequency range from 2 to 40 GHz. Three conformers were assigned and fine splittings caused by the internal rotations of the two terminal methyl groups were analyzed. For the acetyl methyl group CH3C...
Conference Paper
Full-text available
The title molecule 2,6-dimethylanisole (26DMA, C5H3(CH3)2OCH3) is one of the six isomers of dimethylanisole systematically studied by microwave spectroscopy. The spectrum of 26DMA was recorded using a pulsed molecular jet Fourier transform spectrometer. The experimental part was supported by quantum chemical calculations carried out at the B3LYP/6−...
Poster
Full-text available
Introduction For many years, internal rotation has been subject of considerable interest to both chemists and physicists. Studies of potential functions, barrier heights, stability of rotational isomers, and ring conformations provide basic information for testing and improving methods to understand the causes of internal rotation. Quantum chemical...
Article
The microwave spectrum of 3,4-dimethylanisole, a molecule containing three methyl groups allowing for internal rotation, was recorded using a pulsed molecular jet Fourier transform microwave spectrometer operating in the frequency range from 2.0 to 26.5 GHz. Quantum chemical calculations yielded two conformers with a trans and a cis configuration o...
Article
Full-text available
The microwave spectrum of 4-hexyn-3-ol, CH3-C≡C-CH(OH)-CH2CH3, was recorded in the frequency range of 2-26.5 GHz by molecular jet Fourier transform microwave spectroscopy. The conformational analysis based on quantum chemical calculations yielded nine conformers exhibiting C1 symmetry, of which three could be assigned in the experimental spectrum....
Conference Paper
Full-text available
S-Phenyl thioacetate belongs to the thio analogs of the class of unsaturated acetates, which were well-investigated using microwave spectroscopy e. g. butadienyl acetate [1], vinyl acetate [2], and isopropenyl acetate [3]. In contrary to the planar butadienyl and vinyl acetate, isopropenyl acetate has a non-planar structure. This leads to a signifi...
Article
Full-text available
Internal rotation is a fundamental motion of end-standing methyl groups that provides important insight in the molecular physics of isolated molecules. The barrier heights of such large amplitude motions are highly sensitive to their molecular and electronic environment. Until now, it is still not possible to accurately determine barrier heights us...
Article
The rotational spectra of two conformers of pentan-2-one (also known as methyl propyl ketone) were recorded in the frequency range from 2 to 40 GHz using two molecular jet Fourier transform microwave spectrometers. Fine splittings due to the internal rotations of the acetyl methyl group CH3CO– and the butyryl methyl group –COCH2CH2CH3 were resolved...
Article
The microwave spectrum of m-methylanisole (also known as 3-methylanisole, or 3-methoxytoluene) was measured using a pulsed molecular jet Fourier transform microwave spectrometer operating in the frequency range of 2–26.5 GHz. Quantum chemical calculations predicted two conformers with the methoxy group in trans or cis position related to the ring m...
Article
To determine the structural properties of 2,3‐dimethyl‐anisole, a multidisciplinary approach was carried out where gas phase rotational spectroscopy recorded from 2 to 26.5 GHz using a pulsed molecular jet Fourier transform microwave spectrometer was combined with solid state X‐ray diffraction. Both methods revealed that only one conformer with a h...
Article
The microwave spectrum of 2,5-dimethylfuran was recorded using two pulsed molecular jet Fourier transform microwave spectrometers which cover the frequency range from 2 - 40 GHz. The internal rotations of two equivalent methyl tops with a barrier height of approximately 439.15 cm⁻¹ introduce torsional splittings of all rotational transitions in the...
Article
The conformational analysis of 2-methyl-1,3-dithiolane using quantum chemical calculations at some levels of theory yielded only one stable conformer with envelope geometry. However, other levels of theory indicated two envelope conformers. Analysis of the microwave spectrum recorded using two molecular jet Fourier transform microwave spectrometers...
Article
The Fourier transform microwave spectrum of p-methyl anisole, CH3C6H4OCH3, was measured in the frequency range from 2 to 26.5GHz under molecular jet conditions. The conformational analysis yielded only one stable conformer, in which all heavy atoms are co-planar, and which was identified after analyzing the spectrum by comparison with the results f...
Poster
Full-text available
Upper layer of the interactive poster. For further information about the results (fits and experimental values were given as a second layer) please contact the authors.
Conference Paper
Full-text available
Microwave spectroscopy is a powerful tool for determining molecular structures and internal rotation effect. Previous studies on derivatives of anisole have shown that in spite of relatively rigid structures, the internal rotation arising from the ring methyl groups is a challenging task, especially if more than one methyl group exists on the ring...
Article
Full-text available
The Inside Cover picture shows the excellent agreement between the experimental (cyan) and theoretical rotational spectrum (red) of o-methyl anisole in the gas phase. The analysis of torsional splittings from the internal rotation of the ring methyl group yields a three-fold potential with a barrier height of 444 cm⁻¹. More information can be found...
Article
The microwave spectrum of o-methyl anisole (2-methoxytoluene), CH3OC6H4CH3, has been measured using a pulsed molecular jet Fourier transform microwave spectrometer operating in the frequency range 2 - 26.5 GHz. Conformational analysis using quantum chemical calculations at the MP2/6-311++G(d,p) level of theory yields only one stable conformer with...
Article
Phenyl formate has been investigated by molecular jet Fourier-transform microwave spectroscopy in the frequency range from 2 to 26.5 GHz. Quantum chemical calculations at the MP2/6-311++G(d,p) level of theory indicate that this molecule does not have a plane of symmetry at equilibrium, and that the phenyl ring performs a large amplitude tunneling m...
Article
The broadband rotational spectrum of methyl butyrate from 8-18 GHz, recorded using a chirp-pulsed Fourier transform microwave (FTMW) spectrometer, was combined with high resolution FTMW measurements over the 2-26.5 GHz region to provide a comprehensive account of its microwave spectrum under jet-cooled conditions. Two low-energy conformers, one wit...
Article
The rotational spectrum of 3-pentyn-1-ol, CH3−C≡C−CH2CH2OH, was measured using a molecular beam Fourier transform microwave spectrometer operating in the frequency range from 2 to 26.5 GHz. A two-dimensional potential energy surface was calculated at the MP2/6-311++G(d,p) level of theory for a conformational analysis, yielding five conformers. The...
Article
The gas phase structure of n-propyl acetate was determined using molecular beam Fourier transform microwave spectroscopy from 2 to 40 GHz supplemented by quantum chemical calculations. The experimental spectrum revealed only one conformer with trans configuration and C1 symmetry. Torsional splittings occurred for each rotational transition due to t...
Article
The molecular beam Fourier transform microwave spectra of 2-acetyl-5-methylfuran were recorded in the frequency range 2-26.5 GHz. Quantum chemical calculations calculated two conformers with a trans and a cis configuration of the acetyl group, both of which were assigned in the experimental spectrum. All rotational transitions split into quintets d...
Article
The microwave spectra of two conformers of N,N-diethylpropionamide were recorded using a molecular beam Fourier transform microwave spectrometer operating in the frequency range 2-26.5 GHz. Hyperfine splittings arising from the (14)N quadrupole coupling effect were observed and analyzed. Fits using a rigid rotor model with centrifugal distortion co...