Note: Cold spectra of the electronic transition A(2)Σ(+)-X(2)Π of N2O(+) radical: High resolution analysis of the bands 000-100, 100-100, and 001-101

STARGATE: A new instrument for high-resolution photodissociation spectroscopy of cold ionic species

Spectroscopy of transient anions and radicals by gated and accelerated time-of-flight experiment is a new spectrometer developed in UCLouvain. This instrument measures high-resolution photodissociation spectra of mass-selected ions by the combination of a time-of-flight spectrometer including a specific gating, bunching, and re-referencing unit with a nanosecond pulsed dye laser, a pulsed deflection, and an energy selector. The ionic species are generated in a supersonic jet expansion by means of an electric discharge or by the impact of electrons coming from an electron gun. The versatility of the molecular systems that can be addressed by this instrument is illustrated by the presentation of mass spectra of cations, anions, and ionic clusters formed from different gas mixtures and backing pressures. The high-resolution spectrum of the A~²Σ⁺(002)←X~²Π_3/2(000) and A~²Σ⁺(002)←X~²Π_1/2(000) rovibronic bands of N₂O⁺ has been measured and analyzed to provide refined molecular parameters in the A~²Σ⁺(002) upper state. The A~²Σ⁺(002)←X~²Π_3/2(000) band has been used to evaluate the quality of the experimental setup in terms of rotational temperature, time of measurement for certain signal to noise ratio, and the accuracy of the determination of the wavenumber scale.

PFI-ZEKE-photoelectron spectroscopy of N2O using narrow-band VUV laser radiation generated by four-wave mixing in Ar using a KBBF crystal

A new nonlinear optical scheme relying on sum-frequency mixing in a KBe₂BO₃F₂ crystal has been used to generate intense, broadly tunable, narrow-bandwidth, coherent vacuum-ultraviolet (VUV) radiation beyond 16 eV by resonance-enhanced four-wave mixing in Ar. The VUV radiation was used to record high-resolution pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the N₂O⁺ A⁺ ← N₂O X photoionizing transition in the wave-number range from 132 000 cm^-1 to 135 000 cm^-1. The rotational structure of almost all vibrational levels of the A⁺ state with vibrational term values up to 2700 cm^-1 could be resolved, and improved values of the first two adiabatic ionization energies of N₂O, corresponding to the formation of the X^{+ 2}Π_3/2(000) J⁺ = 3/2 and A^{+ 2}Σ⁺(000) N⁺ = 0 levels of N₂O⁺ from the X ¹Σ⁺(000) J″ = 0 ground state [103 969.30(12) cm^-1 and 132 197.70(12) cm^-1, respectively], were derived. The rotational intensity distributions of the bands were found to depend strongly on the value of the vibrational angular momentum of the ionic levels. The vibrational structure is discussed in terms of previously reported effective-Hamiltonian analyses.