Rotational state distribution of N2+ produced from N2 or N2O observed by a laser–synchrotron radiation combination technique

Pump–probe spectroscopy combined with laser and synchrotron radiation is performed to study the ionization and dissociation dynamics of N2 and N2O in the extreme ultraviolet energy region. The N2+(X 2Σ+g, v, N) ion produced from N2 or N2O by synchrotron radiation excitation is detected by laser-induced fluorescence (LIF) spectroscopy. To increase the number density of ions produced by synchrotron radiation photoexcitation, a cylindrical ion trap cell is employed. The effect of thermalization on the internal state distributions of N2+ ion can be ignored in the ion trap. The rotational structure of the electronic excitation B 2Σ+u, v′=0, N′ ← X 2Σ+g, v″=0, N″ of N2+ produced from N2 is clearly resolved by using a narrow-bandwidth Ti:sapphire laser. The yield curves for N2+(X 2Σ+g, v=0, 1) are also measured as a function of the photon energy of the synchrotron radiation. The rotational temperature of N2+(X 2Σ+g, v=0) produced from N2O+(B 2Π) is determined from a LIF spectrum to be in the range 200–230 K. The analysis based on the impulsive model indicates that the equilibrium bond angle of the vibrational ground state of N2O+(B 2Π) is >160°.