Characterizing the origin band spectrum of isoquinoline with resonance enhanced multiphoton ionization and electronic structure calculations.

We report the experimental resonance enhanced multiphoton ionization spectrum of isoquinoline between 315 and 310 nm, along with correlated electronic structure calculations on the ground and excited states of this species. This spectral region spans the origin transitions to a π-π* excited state, which previous work has suggested to be vibronically coupled with a lower lying singlet n-π* state. Our computational results corroborate previous density functional theory calculations that predict the vertical excitation energy for the n-π* state to be higher than the π-π* state; however, we find an increase in the C-N-C angle brings the n-π* state below the energy of the π-π* state.

Singlet O from Ultraviolet Excitation of the Quinoline-O Complex.

We report results from experiments with the quinoline-O complex, which was photodissociated using light near 312 nm. Photodissociation resulted in formation of the lowest excited state of oxygen, O a Δ, which we detected using resonance enhanced multiphoton ionization and velocity map ion imaging. The O ion image allowed for a determination of the center-of-mass translational energy distribution, (), following complex dissociation.

NO (A) Rotational State Distributions from Photodissociation of the N-NO Complex.

We have recorded the resonance-enhanced multiphoton ionization spectrum for NO (A) products from photodissociation of the N-NO complex. We made measurements at excitation energies ranging from 28 to 758 cm above the threshold to produce NO (A) + N (X) products, and the resulting spectra reveal the NO (A) rotational states formed during dissociation, allowing us to determine the rotational state distribution. At the lowest available energies, 28 and 50 cm above threshold, we observed contributions from NO (A) rotational states that exceed the available energy and must originate from excitation due to hotbands of the complex.

Anisotropy Measurements from the Near-Threshold Photodissociation of the N-NO Complex.

We have used velocity map ion imaging to measure the angular anisotropy of the NO (A) products from the photodissociation of the N-NO complex. Our experiment ranged from 108 to 758 cm above the threshold energy to form NO (A) + N (X) products, and these measurements reveal, for the first time, a strong angular anisotropy from photodissociation. At 108 cm above the photodissociation threshold, we observed NO (A) photoproducts recoil preferentially perpendicular to the laser polarization axis with an average anisotropy parameter, β = -0.