Dissociation pathways in the cysteine dication after site-selective core ionization.

Area of Science:

• Atomic and Molecular Physics
• Chemical Physics
• Surface Science

Background:

• Cysteine, an important amino acid, plays crucial roles in biological systems.
• Understanding molecular fragmentation following core-ionization is vital for fields like radiation chemistry and molecular imaging.
• Previous studies have explored core-ionization of small molecules, but detailed investigations on amino acids are less common.

Purpose of the Study:

• To investigate the site-selective dissociation dynamics of the amino acid cysteine following core-ionization.
• To identify and characterize various dissociation channels of cysteine dications.
• To elucidate the roles of nuclear motion and Auger processes in fragmenting core-ionized cysteine.

Main Methods:

• Utilizing a photoelectron-ion-ion coincidence spectroscopy technique.
• Performing core-ionization of cysteine by targeting specific atomic orbitals (O 1s, N 1s, C 1s, S 2p).
• Analyzing the kinetic energies and correlations of fragment ions to determine dissociation pathways.

Main Results:

• Several distinct dissociation channels were identified for core-ionized cysteine.
• A significant site-selective dependence was observed in the fragmentation patterns.
• Evidence suggests that nuclear motion in the core-ionized state and subsequent Auger decay contribute to the observed selectivity.

Conclusions:

• The fragmentation of core-ionized cysteine is strongly dependent on the initial ionization site.
• Both nuclear dynamics and the nature of the Auger decay significantly influence the final dissociation products.
• This study provides detailed insights into the complex fragmentation mechanisms of biologically relevant molecules.