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 -> 1pi* 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 gamma than in isolated N2. A clear correlation between gamma 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 pi* orbital into the matrix.