Publications by Thomas Rizzo | EPFL Graph Search

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Infrared-optical double resonance prepares HOOH molecules in single rotational levels of the 6-nu(OH), 5-nu(OH) + nu(OOH), 5-nu(OH) + nu(OO), and 4-nu(OH) + nu(OH), vibrational states which range from 3 to 2287 cm-1 of excess energy above the unimolecular dissociation threshold. Laser-induced fluorescence probes the nascent OH rotational state distributions from the decomposition of rovibrationally selected reactants. The nascent rotational state distributions reveal that both OH spin-orbit states can be po

The spectroscopy of amide I vibrations has become a powerful tool for exploring protein structure and dynamics. To help with spectral interpretation, it is often useful to perform molecular dynamics (MD) simulations. To connect spectroscopic experiments to simulations in an efficient manner, several researchers have proposed “maps,” which relate observables in classical MD simulations to quantum spectroscopic variables. It can be difficult to discern whether errors in the theoretical results (compared to ex

We describe a new apparatus that combines pulsed laser excitation in a molecular beam with surface-science methods for preparation of clean single-crystal surfaces and detection of adsorbates to enable state-selected studies of gas-surface reaction dynamics. Reactant molecules are prepared in specific vibrationally excited states via overtone pumping using tunable, narrow-band laser radiation. The collision-free environment of the molecular beam prevents relaxation of the prepared molecules before impact on

In this work we use laser-induced population transfer techniques to study the conformational isomerization of a helical peptide, Ac-Phe-(Ala)5-LysH+, in a cold ion trap. In one scheme, called IR-UV hole-filling spectroscopy, a single conformation is select ...

We report state resolved sticking coefficients for highly vibrationally excited CH4 on Ni(100) at well-defined kinetic energies in the range of 12-72 kJ/mol. Incident methane molecules are prepared by pulsed laser radiation in single rovibrational levels of the first overtone of the antisymmetric stretch (2nu(3)) at 6004.69 cm(-1) and collided at normal incidence with a clean Ni(100) single crystal. We find that the vibrational excitation enhances the reaction probability by a factor 100 at an incident tran

The dissociation of methane on a nickel catalyst is a key step in steam reforming of natural gas for hydrogen production. Despite substantial effort in both experiment and theory, there is still no atomic-scale description of this important gas-surface reaction. We report quantum state-resolved studies, using pulsed laser and molecular beam techniques, of vibrationally excited methane reacting on the nickel (100) surface. For doubly deuterated methane (CD2H2), we observed that the reaction probability with

We use infrared-optical double resonance excitation, together with laser induced fluorescence (LIF) product detection, to measure rotationally resolved vibrational overtone spectra of hydrogen peroxide at energies up to 4500 cm(-1) above the O-O dissociation threshold. The spectroscopic constants obtained from such spectra help characterize the potential energy surface and provide a stringent test for any theoretical representation thereof. Line profiles of individual rovibrational features provide informat

Laser light is an invaluable tool for detailed experimental studies of chemical reactions. The ability to prepare reagent molecules in specific quantum states and to resolve the quantum state distribution of reaction products using laser radiation has been key to the field of chemical reaction dynamics, which studies chemistry at a fundamental microscopic level. Today, state-resolved experiments are common for unimolecular and bi-molecular reactions in the gas phase, but equivalent measurements for gas/surf

We use infrared-visible double resonance overtone excitation to promote HOCl molecules to single, well-characterized rotational levels of high OH stretching states just above the HOCl-->HO+Cl dissociation threshold on the ground potential energy surface. Double resonance spectra are monitored by laser induced fluorescence detection of the OH dissociation products. We present here the results obtained in the 6 nu(1) region of (HOCl)-Cl-35 where we have studied states with J ranging from 4 to 25, K-a from 0 t

The high isomeric complexity of glycans makes them particularly difficult to analyze. While ultra-high-resolution ion mobility spectrometry(IMS) can offer rapid baseline separation of many glycan isomers,their unambiguous identification remains a challengi ...

To better understand the complex photophysics of the amino acid tryptophan, which is widely used as a probe of protein structure and dynamics, we have measured electronic spectra of protonated, gas-phase tryptophan solvated with a controlled number of wate ...

Double-resonance vibrational overtone excitation spectra of small molecules, in combination with laser-induced fluorescence product detection, provide information on both their energetics and intramolecular energy redistribution dynamics. Application of this approach to measure OH stretch overtone spectra of HOOH and NH2OH near their dissociation threshold provides estimates of the O-O and N-O bond energies of 17051.8 +/- 4 cm(-1) and 21 620 +/- 20 cm(-1) respectively. In symmetrical molecules, such as HOOH

We report here infrared spectra of protonated and lithiated valine with varying degrees of hydration in the gas phase and interpret them with the help of DFT calculations at the B3LYP/6-31++G** level. In both the protonated and lithiated species, our resul ...

We have measured a vibrationally-resolved UV spectrum of doubly-protonated gramicidin S (GS) in the gas phase and, subsequently, a highly-resolved, conformer-specific infrared spectra in the 6 μm fingerprint region, using a cold ion trap in combination wit ...

A simplified formulation of the harmonic reaction path Hamiltonian (RPH) approach is used to calculate mode specific tunneling splittings and stereomutation times in (CH3OH)-C-12 and (CH3OH)-C-13. The experimental torsional spectrum is very well reproduced, as well as the few known isotope shifts. The mode specific changes in tunneling splitting are investigated for the excitation of fundamentals and OH stretching overtones. Good agreement between experiment and the RPH model is obtained, except for excitat

A joint experimental and first-principles quantum chemical study of the vibration-rotation states of the water molecule up to its first dissociation limit is presented. Triple-resonance, quantum state selective spectroscopy is used to probe the entire ladd ...

An infrared-optical double resonance scheme simplifies the room temperature 6-nu-(OH) vibrational overtone spectrum of hydrogen peroxide and prepares highly excited reactant molecules in single rotational states for unimolecular reaction studies. First, an optical parametric oscillator excites the OH asymmetric stretch (nu-5) and selects a single or small subset of rotational states. A visible dye laser pulse then promotes molecules from v(OH) = 1 to V(OH) = 6 where they subsequently dissociate to produce t

Determining the conformation of biological molecules is key for understanding their function. The recent combination of mass spectrometry, cryogenic ion traps, and laser spectroscopy is providing new methods to interrogate individual conformations of pepti ...

We describe here a study of the spectroscopy of two peptides that we expect to be helical, Ac-Phe-(Ala)5-Lys-H+ and Ac-Phe-(Ala)10-Lys-H+, and one that we expect to be globular, Ac-Lys(H+)-Phe-(Ala)10, with the goal of identifying spectral features charact ...

We report UV photodissociation (UVPD) and IR-UV double-resonance spectra of 1,2-dimethoxybenzene (DMB) complexes with alkali metal ions, M+•DMB (M = Li, Na, K, Rb, and Cs), in a cold 22-pole ion trap. The UVPD spectrum of the Li+ complex shows a strong ori ...

Thomas Rizzo

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Product energy partitioning in the unimolecular decomposition of vibrationally and rotationally state‐selected hydrogen peroxide

Assessment of amide I spectroscopic maps for a gas-phase peptide using IR-UV double-resonance spectroscopy and density functional theory calculations

Molecular-beam/surface-science apparatus for state-resolved chemisorption studies using pulsed-laser preparation

IR-induced conformational isomerization of a helical peptide in a cold ion trap

Surface reactivity of highly vibrationally excited molecules prepared by pulsed laser excitation: CH4 (2 nu(3)) on Ni(100)

Vibrational mode-specific reaction of methane on a nickel surface

State-to-state studies of intramolecular energy transfer in highly excited HOOH(D): Dependencies on vibrational and rotational excitation

Quantum state resolved studies of gas/surface reaction dynamics

The spectroscopy and intramolecular vibrational energy redistribution dynamics of HOCl in the v(OH)=6 region, probed by infrared-visible double resonance overtone excitation

Using Hadamard Transform Multiplexed IR Spectroscopy Together with a Segmented Ion Trap for the Identification of Mobility-Selected Isomers

Microsolvation effects on the excited state dynamics of protonated tryptophan

State-to-state studies of intramolecular dynamics and unimolecular reactions

Infrared spectroscopy of hydrated amino acids in the gas phase: protonated and lithiated valine

Highly-resolved Spectra of Gas-phase Gramicidin S: A Benchmark for Peptide Structure Calculations

Ab initio calculations of mode selective tunneling dynamics in (CH3OH)-C-12 and (CH3OH)-C-13

State-selective spectroscopy of water up to its first dissociation limit

Rotationally resolved vibrational overtone spectroscopy of hydrogen peroxide at chemically significant energies

Cryogenic Methods for the Spectroscopy of Large, Biomolecular Ions

Spectroscopy and Conformational Preferences of Gas-Phase Helices

UV and IR spectroscopy of cold 1,2-dimethoxybenzene complexes with alkali metal ions