Broadening of vibrational levels in X-ray absorption spectroscopy of molecular nitrogen in compound semiconductors

We have used high-resolution near-edge X-ray absorption fine structure spectroscopy to study the N 1s → 1π∗ resonance of N2 trapped below the surface of several compound semiconductors. The vibrational fine structure, observed from all samples under consideration, exhibits substantially larger lifetime linewidth Γ than in isolated N2. A clear correlation between Γ and the lattice constant of the host matrix has been found, indicating that the broadening of vibrational levels is governed by a finite probability of the electron to escape from the π∗ orbital into the matrix.