Asymmetry of Departing Fragment Ion in theK-Shell Excitation ofn2

The angular distribution of departing ${\mathrm{N}}^{+}$ ions from ${\mathrm{N}}_2$ stimulated by $K$-shell photoexcitation has been measured by use of a time-of-flight mass spectrometer. A detailed analysis of the flight-time spectra shows that at 401 eV, i.e., the resonance transition from $1s{\sigma }_{\mathrm{u}}$ to $2p{\pi }_{\mathrm{g}}$, the asymmetry parameter $\beta$ is close to -1. Between 405 and 410 eV, $\beta$ shows an oscillatory variation due to the core-electron excitations to the Rydberg states. In the ${\sigma }_{\mathrm{u}}$-type shape resonance, $\beta$ is larger than 0. The results obtained are discussed in relation to the characteristics of the $K$-shell excited states.