Dynamic stabilization in 1sigma(u)-->1pi(g) excited nitrogen clusters

Area of Science:

• Physics
• Chemistry
• Materials Science

Background:

• Molecular nitrogen (N2) spectroscopy provides fundamental insights into chemical bonding and electronic structure.
• Understanding nitrogen clusters is crucial for modeling atmospheric phenomena and chemical processes.
• Synchrotron radiation enables high-resolution studies of electronic excitations in molecules and clusters.

Purpose of the Study:

• To investigate the 1s near-edge X-ray absorption fine structure (XAFS) of molecular nitrogen and nitrogen clusters.
• To analyze the core-to-valence electronic excitations in N2 molecules within clusters.
• To determine the influence of cluster formation on the electronic and vibrational properties of N2.

Main Methods:

• High-resolution 1s near-edge X-ray absorption spectroscopy was performed on molecular nitrogen and variable-size nitrogen clusters.
• Monochromatic synchrotron radiation from the BESSY-II storage ring was utilized for excitation.
• Vibrational resolution was achieved to analyze spectral features.

Main Results:

• A distinct redshift of 6+/-1 meV was observed in the 1sigma(u)-->1pi(g) core-to-valence excitation band of nitrogen clusters compared to isolated N2 molecules.
• The vibrational structure and linewidths of the excitation band remained largely unchanged in the clusters.
• The observed spectral shift was attributed to dynamic stabilization of excited molecules within the cluster environment.

Conclusions:

• Core-hole localization in the low-symmetry cluster field induces a dynamic dipole moment, leading to stabilization of excited N2 molecules.
• Intermolecular interactions in nitrogen clusters are altered upon electronic excitation compared to the ground state.
• The observed spectral shifts are anticipated to be a general phenomenon in molecular clusters and condensed phases.