Femtosecond photoelectron imaging on pyrazine: Spectroscopy of 3s and 3p Rydberg states

Abstract

Two-color and one-color resonance enhanced multiphoton ionization photoelectron spectroscopies (REMPI–PES) have been applied to Rydberg states (n=3) of jet-cooled pyrazine. The 3s and 3p members of Rydberg series converging to the ground state (n−1) of the cation and the 3s member of a Rydberg series converging to an excited state of the cation (π−1) were observed. The photoelectron angular distributions (PADs) measured via the 3s(n−1) state drastically differed for the two-color and one-color REMPI experiments. This behavior is ascribed to different molecular axis alignments created by the two-photon excitation schemes. The PADs were also used to discriminate between the different Rydberg series.

Femtosecond Time‐Resolved Photoelectron Spectroscopy

“…The photoelectron imaging method allowed identification of the intermediate states resonances as 3s(n -1 ) and 3p(n -1 ) Rydberg series. In contrast with the earlier studies of excited-state dynamics in pyrazine, 145 pyridazine interestingly showed no evidence of intersystem crossing dynamics (i.e., no triplet-state formation). Analysis of the PADs indicated mostly p-wave emission from the 3s state, whereas the 3p photoemission was comprised of a mixture of partial waves.…”

“…145 In that paper, the authors investigated in detail the spectroscopy and dynamics of the 3s and 3p Rydberg states involved in their previous two-probe photon ionization studies of the pyrazine S 1 state. 135 Through variation of the pump laser wavelength from 401 to 330 nm, series of singlet 3s(π -1 ), triplet 3s(n -1 ), and triplet 3pA(n -1 ) Rydberg states with sub-ps lifetimes were observed.…”

“…A more complete discussion of the ionization dynamics of the pyrazine 3s and 3p Rydberg states followed in 2001. 145 As discussed in section 5.6, in 2000 Hayden and co-workers used the 3D coincidence-imaging spec- troscopy (CIS) method to observe the evolution of molecular-frame PADs during the photodissociation of NO 2 . 116 In 2002, Hayden and co-workers studied the S 2 1 E′ f S 1 1 A 1 ′ internal conversion in triethylenediamine (DABCO) using the CIS method.…”

Nonadiabatic Electronic Dynamics in Isolated Molecules and in Solution Studied by Ultrafast Time–Energy Mapping of Photoelectron Distributions

“…28,64,65 After exciting pyrazine to the zero vibrational level in S 1 , we observed two-photon ionization from the S 1 and T 1 states using the 400 nm probe pulse, in which ionization was enhanced by accidental resonance with the Rydberg states. 64 The photoelectron signal intensities of S 1 and T 1 in Figure 10b exhibit respectively a gradual decay and growth as a function of time, in which characteristic spikes due to A(t) appeared (The S 1 state is probed via both 3s and 3p Rydberg states, 54,57 which exhibit opposite sign of the rotational coherence spikes). Similar signatures of A(t) is also seen in the photoelectron angular anisotropies (represented by ¢ 20 /¢ 00 in this case) in Figure 10c.…”

“…The three peaks in the energy range of 1.52.7 eV are of the 3s, 3p z , and 3p y Rydberg states. 54,57 The distribution in the 02 eV range is due to photodissociation from higher valence states excited with 5½, so that the photoelectron kinetic energy diminishes rapidly as the vibrational wave packet moves away from the Franck Condon region. Let us examine the dynamics in comparison with the internal conversion in pyrazine.…”