Time resolved detection of the S(1D) product of the UV induced dissociation of CS2

Abstract

The products formed following the photodissociation of UV (200 nm) excited CS 2 are monitored in a time resolved photoelectron spectroscopy experiment using femtosecond XUV (21.5 eV) photons. By spectrally resolving the electrons we identify separate photoelectron bands related to the CS 2 + hν −→ S( 1 D) + CS and, CS 2 + hν −→ S( 3 P) + CS dissociation channels which show different appearance and rise times. The measurements show that there is no delay in the appearance of the S( 1 D) product contrary to the results of J. Chem. Phys. 147, 013932 (2017). Analysis of the photoelectron yield associated with the atomic products allows us to obtain a S( 3 P)/S( 1 D) branching ratio and the rate constants associated with dissociation and intersystem crossing rather than the effective lifetime observed through the measurement of excited state populations alone.

Multichannel photodissociation dynamics in CS2 studied by ultrafast electron diffraction

“…This compares with the unweighted trajectories which give a branching ratio of 1 : 1.9 with a remainder bound contribution of 24% at t = 1 ps. Both the biased and the unbiased branching ratios are in reasonable agreement with recent time resolved photoelectron spectroscopy measurements, 4,36 and those measured in nanosecond experiments measuring the final products 37–43 which provide values around 1 : 2.5 and 1 : 3 respectively. The 1 : 3 ratio from the nanosecond experiments is based on an average of a number of measurements which have provided varied estimates between 4 : 1 and 1 : 6.…”

Ultrafast Extreme Ultraviolet Photoelectron Spectroscopy of Nonadiabatic Photodissociation of CS2 from 1B2 (1Σu+) State: Product Formation via an Intermediate Electronic State

“…Previously, TRPEI study by Horio et al suggested that S­( 1 D 2 ) reaction products appear after a certain latency time, which suggests the presence of an intermediate state for the singlet dissociation channel. In this sense, our conclusion is consistent with that of Horio et al Minns and colleagues proposed a slightly different kinetic model, which assumes that the singlet reaction products are generated directly from 1 B 2 ; however, we found that the experimental data presented here cannot be well-explained with their model. , They measured similar time profiles with the cross-correlation time of 180 fs and performed the analysis without considering molecular signals. As presented in section S6 of the Supporting Information, when the experimental data shown in Figure c are convoluted with a Gaussian function with a full width at half-maximum (fwhm) of 180 fs, the time profiles become much smoother and the position of initial signal rise become elusive.…”

“…As presented in section S6 of the Supporting Information, when the experimental data shown in Figure c are convoluted with a Gaussian function with a full width at half-maximum (fwhm) of 180 fs, the time profiles become much smoother and the position of initial signal rise become elusive. Thus, we believe the difference between the two studies largely originates from the low temporal resolution and the lack of consideration of molecular signals. , …”

“…Understanding the mechanistic details of these complex electronic dynamics is one of the main research subjects in molecular reaction dynamics. , UV photodissociation of carbon disulfide from the 1 B 2 ( 1 Σ u + ) state is known to produce both singlet and triplet products (Figure )­ Interestingly, the spin-forbidden channel (eq 1b) has a greater quantum yield than the spin-allowed channel (eq 1a). − This reaction has been studied using a plethora of experimental methods; however, the mechanism involved is yet to be understood. − In this Letter, we report time-resolved extreme UV (EUV) photoelectron spectroscopy (TRPES) with the pump–probe cross-correlation time of 48 fs, which was obtained by the combination of an ultrafast deep UV (6.2 eV; 200 nm) laser based on filamentation four-wave mixing (FFWM) − and an EUV (21.7 eV) laser based on high-order harmonic generation (HHG). − As discussed later, a high temporal resolution and signal-to-noise ratio are crucial for extraction of dynamical information such as the nuclear wave packet motions in the 1 B 2 state, electronic relaxation from 1 B 2 to intermediate electronic state(s), and subsequent dissociation into the singlet and triplet reaction products.…”

Transient vibration and product formation of photoexcited CS2 measured by time-resolved x-ray scattering

“…Experimental techniques used to study this CS 2 reaction cover a wide range. Photoelectron spectroscopies 11,12,14,[18][19][20][21] are generally sensitive to the instantaneous electronic state of the system. Ion momentum imaging with state-selective resonanceenhanced multi-photon ionization (REMPI) has yielded information on the dissociation velocity distribution of the various breakup channels 22,23 .…”