Vibrational dynamics of formic acid and its dimer: FTIR and Raman jet spectroscopy and theory

Abstract

FTIR and Raman jet spectroscopy and theory DISSERTATION zur Erlangung des mathematisch-naturwissenschaftlichen Doktorgrades "Doctor rerum naturalium" der Georg-August-Universität Göttingen im Promotionsprogramm Chemie der Georg-August University School of Science (GAUSS) vorgelegt von ARMAN NEJAD aus Münster Göttingen 2022 Danksagung Die vorliegende Arbeit wurde im Januar 2022 als Dissertation an der Fakultät für Chemie der Georg-August-Universität Göttingen eingereicht. Diese Arbeit hätte nicht entstehen können ohne den entscheidenden und prägenden Einfluss auf meinen wissenschaftlichen Werdegang durch meinen Erstgutachter und Mentor Prof. Dr. Martin Suhm, der mich von einer Promotion im Fach Chemie überzeugt hat und das interdisziplinäre Verknüpfen von Physik und Chemie, Experiment und Theorie ermutigte und förderte sowie mir stets mit Rat und Tat zur Seite stand. Ihm gilt mein ganz besonderer Dank. Für die Übernahme des Zweitgutachtens möchte ich Prof.

Vibrational infrared and Raman spectra of HCOOH from variational computations

“…This work is a continuation of ref. 1 and was motivated by a systematic experimental effort [2][3][4][5] to acquire the infrared and Raman vibrational spectrum of the formic acid monomer to set experimental benchmarks and to challenge computational quantum dynamics methodologies. [6][7][8][9][10][11][12][13] In the present work, we aim to make progress with a complete quantum dynamical characterization of this fiveatom molecule.…”

Vibrational infrared and Raman spectrum of HCOOH from variational computations

“…This work is a continuation of Ref. 1 and has been motivated by a systematic experimental effort [2][3][4][5] to measure the infrared and Raman vibrational spectrum of the formic acid monomer to set experimental benchmarks and to challenge computational quantum dynamics methodologies. [6][7][8][9][10][11][12][13] In the present work, we aim to make progress with a complete quantum dynamical characterization of this five-atomic molecule.…”

Mid-infrared Laser Spectroscopy of Jet-Cooled Formic Acid Trimer: Mode-Dependent Line Broadening in the C–O Stretching Region

“…A recent reanalysis of the fingerprint region revealed a multitude of new vacuum-isolated F(FF) bands in the jet-cooled spectra of HCOOH 14 and its three deuterated isotopologues, 9 increasing the number of low-resolution vibrational band centers from 4 to a total of 40 [including 26 deuterated ones]. 9,11,13 Its surprisingly high concentration 14 in jet-cooled spectra can be rationalized by space-resolved FTIR imaging which suggests that F(FF) is actively formed from F and (FF) in jet expansions, both of which are abundantly available in the gas phase. 11 The C−O stretching vibrations of formic acid are highly infrared-active, 27 strongly mixed with the CH and OH bends, 28 and their transition wavenumbers are very sensitive 9 toward the isotope composition and the hydrogen bond environment in F n clusters, 14 making them a well-suited target for non-sizeselective IR spectroscopy.…”

“…Since C−H deuteration not only detunes the C−O stretch resonance in (FF) but also shifts the nearby monomer band toward lower wavenumbers, formic-d acid appears to be a promising candidate for the detection of the missing ν 17 . 9 Whereas O−H deuteration further reduces the shift of ν 17 to nearby dimer bands and might complicate the assignment, it might still prove more successful should ν 17 be broadened due to coupling with the double proton exchange. Similarly, if the line broadening of ν 16 reduces upon O−H deuteration, the underlying mechanism might be associated with coupling to the proton transfer, accelerating tunneling to F A (FF) [see Figure 3].…”

“…Measurement of the C–O stretching spectra of (DCOOH) 3 and (HCOOD) 3 might provide further insights. Since C–H deuteration not only detunes the C–O stretch resonance in (FF) but also shifts the nearby monomer band toward lower wavenumbers, formic- d acid appears to be a promising candidate for the detection of the missing ν 17 . Whereas O–H deuteration further reduces the shift of ν 17 to nearby dimer bands and might complicate the assignment, it might still prove more successful should ν 17 be broadened due to coupling with the double proton exchange.…”