0000000000276614
AUTHOR
Kseniya Marushkevich
Conformation resolved induced infrared activity: trans- and cis-formic acid isolated in solid molecular hydrogen
We report combined experimental and theoretical studies of infrared absorptions induced in solid molecular hydrogen by different conformers of formic acid (HCOOH, FA). FTIR spectra recorded in the H(2) fundamental region (4120-4160 cm(-1)) reveal a number of relatively strong trans-FA induced Q-branch absorptions that are assigned by studying both FA-doped parahydrogen (pH(2)) and normal hydrogen (nH(2)) samples. The induced H(2) absorptions are also studied for HCOOD doped nH(2) crystals for both the trans and cis conformers that show resolvable differences. Samples containing90% of the higher energy cis-HCOOD conformer are produced by in situ IR pumping of the OD stretching overtone of tr…
Matrix Isolation and Ab Initio Study of Trans−Trans and Trans−Cis Dimers of Formic Acid
Six trans-trans and five trans-cis dimeric structures of formic acid (HCOOH) are revealed by ab initio calculations. Four trans-trans and two trans-cis dimers are identified in the IR absorption spectra in argon matrices. The trans-cis dimers are obtained by narrow-band IR excitation of the vibrational transitions of the trans-trans dimers. Two trans-trans (tt3 and tt6) and one trans-cis (tc4) dimer are characterized experimentally for the first time. The tunneling decay rates of two trans-cis dimers (tc1 and tc4) are evaluated at different temperatures. A greater lifetime of the trans-cis dimers at elevated temperatures compared to the cis-monomer suggests that the high-energy conformers c…
Vibrational spectroscopy of trans and cis deuterated formic acid (HCOOD): Anharmonic calculations and experiments in argon and neon matrices
The absorption spectra of trans and cis conformers of deuterated formic acid (HCOOD) isolated in argon and neon matrices are analyzed in the mid-infrared and near-infrared spectral regions (7900–450 cm � 1 ). Vibrational excitation by narrow-band IR radiation is used to convert the lower-energy trans conformer to the higher-energy cis form. A large number of overtone and combination bands are identified. The results of anharmonic vibrational calculations (CC-VSCF) for both conformers are reported and compared to the experimental spectra.
Dimers of the Higher-Energy Conformer of Formic Acid: Experimental Observation
We report on the first experimental observation of formic acid dimers composed of two molecules of the higher-energy cis conformer. The cis–cis formic acid dimers are prepared in an argon matrix by selective vibrational excitation of the ground state trans conformer (deuterated form HCOOD) combined with thermal annealing of the matrix at about 30 K. Five cis–cis formic acid dimers are predicted by ab initio calculations (interaction energies from −16.9 to −27.2 kJ molˉ¹), and these structures are used for the assignment of the experimental spectra. Selective vibrational excitation of the obtained cis–cis dimers leads to the formation of several trans–cis dimers, which supports the proposed …