Rotationally resolved photoelectron spectroscopy of hot N2 formed in the photofragmentation of N2O

Vacuum ultraviolet photodissociation dynamics of N2O via the C1Π state: The N(2Dj=5/2, 3/2) + NO(X2Π) product channels

We study the vacuum ultraviolet photodissociation dynamics of N₂O via the C¹Π state by using the time-sliced velocity map ion imaging technique. Images of N(²D_{j=5/2, 3/2}) products from the N atom elimination channels were acquired at a set of photolysis wavelengths from 142.55 to 148.19 nm. Vibrational states of the NO(X²Π) co-fragments were partially resolved in experimental images. From these images, the product total kinetic energy release distributions (TKERs), branching ratios of the vibrational states of NO(X²Π) co-fragments, and the vibrational state specific angular anisotropy parameters (β) have been determined. Notable features were found in the experimental results: the TKERs show that the NO(X²Π) co-fragments are highly vibrationally excited. For the highly vibrationally excited state of NO(X²Π), a bimodal rotational structure is found at all the studied photolysis wavelengths. Furthermore, the vibrational state specific β values of both spin-orbit channels (j = 3/2, 5/2) clearly show a monotonic decrease as the vibrational quantum number of NO(X²Π) increases. These observations suggest that multiple dissociation pathways play a role in the formation of the N(²D_{j=5/2, 3/2}) + NO(X²Π) products: one corresponds to a fast dissociation pathway through the linear state (the C¹Π state) following the initial excitation to a slightly bent geometry in the vicinity of the linear C¹Π configuration, leading to the low rotationally excited components with relatively large β values; the other corresponds to a relatively slow dissociation pathway through the bent C(3¹A') or C(3¹A″) state, leading to moderately rotationally excited NO(X²Π) products with smaller β values.

Photodissociation of nitrous oxide starting from excited bending levels

The photodissociation dynamics of N2O in the wavelength region of 203-205 nm was studied by velocity map ion imaging. A speed resolution of 0.8% was obtained using standard projection imaging and subpixel centroiding calculations. To investigate N2O dissociation starting from the excited bending levels in the ground electronic state, a supersonic molecular beam and an effusive beam were used. The photoabsorption transition probability from the first excited bending level in the wavelength region of 203-205 nm was estimated to be seven times greater than that from the ground vibrational level.

Photoionization dynamics in CS fragmented from CS2 studied by high-resolution photoelectron spectroscopy

The photoionization dynamics of CS have been studied using high-resolution laser photoelectron spectroscopy. The photodissociation of CS2 at ~308 nm results in highly rotationally excited CS in its X1Σ+ singlet ground state, as well as in rotationally cold CS in the excited a3Π triplet state. The ground-state CS fragments are formed together with sulfur in its 3P, 1D, and 1S electronic states; triplet CS is produced in coincidence with ground-state sulfur (3P). In both channels the photoelectron spectra are dominated by Δv = 0 propensity, but transitions involving Δv = 1 and 2 are also observed. Key words: photoelectron spectroscopy, photoionization, photodissociation, excited states, reactive intermediates.