Publication

Structural Melting of an Amino Acid Dimer upon Intersystem Crossing

Thomas Rizzo, Ulrich Lorenz
2014
Journal Articles

Abstract

We present a spectroscopic investigation of the excited-state dynamics of the phenylalanine (Phe)/serine (Ser) protonated dimer in the gas phase. Using an ultraviolet (UV) laser pulse, we promote individual isomers to the S1 state and probe their fate with an infrared (IR) pulse. We find that the S1 state has a lifetime of ?70 ns and undergoes intersystem crossing (ISC) to the T1 state. Time-resolved IR spectra allow us to follow the structural evolution of the dimer. In the S1 state, the different isomers retain the hydrogen-bonding pattern of the ground state. Intersystem crossing triggers a sudden increase of the vibrational energy, so that the dimers can overcome isomerization barriers and explore large parts of the potential energy surface (PES). Their broad IR spectra largely resemble one another and indicate that the dimers adopt a molten structure.

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https://infoscience.epfl.ch/entities/publication/939c6abe-b1de-45ac-aa9d-4a42053bb45f

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Thomas Rizzo, Ulrich Lorenz
2014
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/939c6abe-b1de-45ac-aa9d-4a42053bb45f

About this result

Related concepts (32)

Intersystem crossing

Intersystem crossing (ISC) is an isoenergetic radiationless process involving a transition between the two electronic states with different spin multiplicity. When an electron in a molecule with a singlet ground state is excited (via absorption of radiation) to a higher energy level, either an excited singlet state or an excited triplet state will form. Singlet state is a molecular electronic state such that all electron spins are paired.

Infrared spectroscopy

Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functional groups in solid, liquid, or gaseous forms. It can be used to characterize new materials or identify and verify known and unknown samples. The method or technique of infrared spectroscopy is conducted with an instrument called an infrared spectrometer (or spectrophotometer) which produces an infrared spectrum.

Quantum yield

In particle physics, the quantum yield (denoted Φ) of a radiation-induced process is the number of times a specific event occurs per photon absorbed by the system. The fluorescence quantum yield is defined as the ratio of the number of photons emitted to the number of photons absorbed. Fluorescence quantum yield is measured on a scale from 0 to 1.0, but is often represented as a percentage. A quantum yield of 1.0 (100%) describes a process where each photon absorbed results in a photon emitted.

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