Rotational state distribution of N 2+ produced from N 2 or N 2O observed by a laser–synchrotron radiation combination technique

Abstract

Pump–probe spectroscopy combined with laser and synchrotron radiation is performed to study the ionization and dissociation dynamics of N 2 and N 2O in the extreme ultraviolet energy region. The N 2 +( X 2 Σ + g , v, N) ion produced from N 2 or N 2O 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 N 2 + ion can be ignored in the ion trap. The rotational structure of the electronic excitation B 2 Σ + u , v′=0, N′ ← X 2 Σ + g , v″=0, N″ of N 2 + produced from N 2 is clearly resolved by using a narrow-bandwidth Ti:sapphire laser. The yield curves for N 2 +( X 2 Σ + g , v=0, 1) are also measured as a function of the photon energy of the synchrotron radiation. The rotational temperature of N 2 +( X 2 Σ + g , v=0) produced from N 2O +( B 2 Π ) 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 N 2O +( B 2 Π ) is >160°.