Coherent polyatomic dynamics studied by femtosecond time-resolved photoelectron spectroscopy: Dissociation of vibrationally excited CS2 in the 6s and 4d Rydberg states

Abstract

The dissociation dynamics of the 6s and 4d Rydberg states of carbon disulfide (CS(2)*) are studied by time-resolved photoelectron spectroscopy. The CS(2) is excited by two photons of 267 nm (pump) to the 6s and 4d Rydberg states and probed by ionization with either 800 or 400 nm. The experiments can distinguish and successfully track the time dynamics of both spin [1/2] (upper) and [3/2] (lower) cores of the excited Rydberg states, which are split by 60 meV, by measuring the outgoing electron kinetic energies. Multiple mode vibrational wave packets are created within the Rydberg states and observed through recurrence interferences in the final ion state. Fourier transformation of the temporal response directly reveals the coherent population of several electronic states and vibrational modes. The composition of the wave packet is varied experimentally by tuning the excitation frequency to particular resonances between 264 and 270 nm. The work presented here shows that the decay time of the spin components exhibits sensitivity to the electronic and vibrational states accessed in the pump step. Population of the bending mode results in an excited state lifetime of as little as 530 fs, as compared to a several picosecond lifetime observed for the electronic origin bands. Experiments that probe the neutral state dynamics with 400 nm reveal a possible vibrationally mediated evolution of the wave packet to a different Franck-Condon window as a consequence of Renner-Teller splitting. Upon bending, symmetry lowering from D(infinityh) to C(2v) enables ionization to the CS(2) (+) (B (2)Pi(u)) final state. The dissociation dynamics observed are highly mode specific, as revealed by the frequency and temporal domain analysis of the photoelectron spectra.

Investigation of coupling mechanisms in attosecond transient absorption of autoionizing states: comparison of theory and experiment in xenon

“…Similar quantum beats between bound states have been observed in a recent experiment of neon atoms with attosecond laser pulses [16]. Vibrational quantum beats between decaying Rydberg states have also been previously measured with transient absorption experiments with picosecond lasers [28,29].…”

Field modulation of Rydberg-state populations of NO studied by femtosecond time-resolved photoelectron imaging

“…Interesting phenomena have been reported in past decades in an intense femtosecond laser field, including abovethreshold ionization [4,5], the ac Stark shift [6,7], harmonic generation [5,8], coherent phenomena [9,10], and laser-induced continuum structure [11]. Recently, chemical reaction control has become a hot topic in femtochemistry [6,7,[12][13][14][15].…”

Time-dependent wave packet theoretical study of femtosecond photoelectron spectra and coupling between the A2Σ+ and B2Π states of the NO molecule in a strong laser field

“…Wang et al assigned two peaks centered at 0.82 and 2.35 eV as the 2+1' and 2+2 multi-photon ionizations, which are excited to A 2 Σ + by one-color photons (pump at 408 nm). In the overlap region of the pump and probe lights, the 0.37 eV peak was observed when the intensity of the pump laser was higher than 2 9×10 12 W/cm 2 , which indicates that the Rydberg-valance coupling between the A 2 Σ + and B 2 Π states is a important factor. In this work, the femtosecond PES of NO via 2+1' MPI (pump at 408 nm, probe at 271 nm) has been calculated and compared with the experimental results.…”

“…In the past decade, a number of interesting phenomena in the intense femtosecond laser field, such as above threshold ionization (ATI) [5,6], AC-Stark shift [7][8][9], harmonic generation [10,11], coherent phenomena [12,13], and laser-induced continuum structure [14], have been reported. Recently, control of chemical reaction has become a hot topic infemtochemistry [15,16].…”