Femtosecond pump-probe photoelectron spectroscopy measurements using an extreme ultravioletprobe have been made on the photodissociation dynamics of UV (269 nm) excited CH3I. TheUV excitation leads to population of the 3Q0...
We report a combined experimental and computational study of carbon dioxide activation at gas-phase Ho+ and HoO+ centres. Infrared action spectra of Ho(CO2)n+ and [HoO(CO2)n]+ ion-molecule complexes have been recorded...
Methyl cinnamate (MC) is an ester within the cinnamate family. Recent time-resolved gas-phase studies have suggested that upon excitation to its first singlet ππ* (1 1 ππ*) state, there is initial decay to the lowest lying singlet 1 nπ* (1 1 nπ*) state within 10 ps, en route to trans-cis isomerisation. In the present study, we have implemented time-resolved ion yield (TR-IY) and time-resolved photoelectron spectroscopy (TR-PES) experiments in the gas-phase to precisely determine the lifetime of the 1 1 ππ* state. We found this lifetime to be ∼ 4.5 ps using both TR-IY and TR-PES. MC was also studied in a more complex cyclohexane solution environment, using transient electronic absorption spectroscopy. Along with complementary steady-state irradiation and 1 H NMR studies, these studies demonstrate that trans-cis isomerisation is preserved in the more complex, cyclohexane solution environment.
We present a combined experimental and quantum chemical
study of
gas-phase group 9 metal nitrosyl complexes, M(NO)
n
+ (M = Co, Rh, Ir). Experimental infrared photodissociation
spectra of mass-selected ion-molecule complexes are presented in the
region 1600 cm–1 to 2000 cm–1 which
includes the NO stretch. These are interpreted by comparison with
the simulated spectra of energetically low-lying structures calculated
using density functional theory. A mix of linear and nonlinear ligand
binding is observed, often within the same complex, and clear evidence
of coordination shell closing is observed at n =
4 for Co(NO)
n
+ and Ir(NO)
n
+. Calculations of Rh(NO)
n
+ complexes suggest additional
low-lying five-coordinate structures. In all cases, once a second
coordination shell is occupied, new spectral features appear which
are assigned to (NO)2 dimer moieties. Further evidence
of such motifs comes from differences in the spectra recorded in the
dissociation channels corresponding to single and double ligand loss.
The dissociation dynamics of CH 3 I at three UV pump wavelengths (279 nm, 254 nm, 243 nm) are measured using an extreme ultraviolet probe in a timeresolved photoelectron spectroscopy experiment. The results are compared with previously published data at a pump wavelength of 269 nm, [Phys. Chem. Chem. Phys., 2020, 22, 25695], with complementary photoelectron spectroscopy experiments performed using a multiphoton ionization probe [Phys. Chem. Chem. Phys., 2019, 21, 11142] and with the recent action spectroscopy measurements of Murillo-Sánchez et al. [J. Chem. Phys., 2020, 152, 014304]. The measurements at 279 nm and 243 nm show signals that are consistent with rapid dissociation along the C-I bond occurring on timescales that are consistent with previous measurements. The measurements at 254 nm show a significantly longer excited state lifetime with a secondary feature appearing after 100 fs is indicative of more complex dynamics in the excited state. The timedependence of the changes are consistent with the previously measured multiphoton ionization photoelectron spectroscopy measurements of Warne et al., [Phys. Chem. Chem. Phys., 2019, 21, 11142]. The consistency of the signal appearance across ionization processes suggests that the extended observation time at 254 nm is not an artefact of the previously used multiphoton ionization process but is caused by more complex dynamics on the excited state potential. Whether this is caused by complex vibrational dynamics on the dominant 3 Q 0 state or due to enhanced population and dynamics on the 1 Q 1 state remains an open question.
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