Hydrogen transfer dynamics in a photoexcited phenol/ammonia (1:3) cluster studied by picosecond time-resolved UV-IR-UV ion dip spectroscopy

Abstract

The picosecond time-resolved IR spectra of phenol/ammonia (1:3) cluster were measured by UV-IR-UV ion dip spectroscopy. The time-resolved IR spectra of the reaction products of the excited state hydrogen transfer were observed. From the different time evolution of two vibrational bands at 3180 and 3250 cm(-1), it was found that two isomers of hydrogenated ammonia radical cluster .NH(4)(NH(3))(2) coexist in the reaction products. The time evolution was also measured in the near-IR region, which corresponds to 3p-3s Rydberg transition of .NH(4)(NH(3))(2); a clear wavelength dependence was found. From the observed results, we concluded that (1) there is a memory effect of the parent cluster, which initially forms a metastable product, .NH(4)-NH(3)-NH(3), and (2) the metastable product isomerizes successively to the most stable product, NH(3)-.NH(4)-NH(3). The time constant for OH cleaving, the isomerization, and its back reaction were determined by rate-equation analysis to be 24, 6, and 9 ps, respectively.

Stabilities of nanohydrated thymine radical cations: insights from multiphoton ionization experiments and ab initio calculations

“…a e-mail: s.p.eden@open.ac.uk means of UV irradiation [9,10]. Here we investigate the stabilities of nanohydrated thymine radical cations based on metastable dissociation measurements and ab initio calculations.…”

Electron‐Proton Transfer Mechanism of Excited‐State Hydrogen Transfer in Phenol‐(NH3)n (n=3 and 5)

“…In particular, spectroscopic evidence that the intermediate is a . H(NH 3 ) n radical, not a protonated one, gives strong support to the paradigm shift from ESPT to ESHT; for the latter one two different paths either with a coupled or decoupled migration of the electron and proton are possible (see Figure ) –. Now, ESHT is a de facto standard of the mechanism in gas‐phase photochemistry, and various photochemical mechanisms are redefined by ESHT, such as indole, tryptophan aromatic amino acid cations, and many other systems…”

“…Picosecond time‐resolved IR/NIR (ps‐TRIR/psTRNIR) spectroscopy of PhOH‐(NH 3 ) 5 was performed by utilizing time‐resolved ultraviolet (UV)‐IR/UV‐NIR ion dip spectroscopy, of which the principle has been described elsewhere ,. The excitation scheme is illustrated in Figure .…”

“…S 1 –S 0 electronic transitions of PhOH‐(NH 3 ) n have been reported previously . For clusters with n ≤4, the spectra show well‐resolved structures, which suggest a slow ESHT reaction (24 ps for n= 3) ,. In contrast, PhOH‐(NH 3 ) 5 only gives rise to a broad absorption, which indicates a significant change of the reaction mechanism of ESHT .…”

Single water solvation dynamics in the 4-aminobenzonitrile–water cluster cation revealed by picosecond time-resolved infrared spectroscopy

“…[23][24][25][26] To observe the solvation dynamics of aromatic clusters generated in molecular beams, we have developed the technique of mass-selective three-color tuneable UV-UV'-IR picosecond timeresolved infrared (ps TRIR) pump-probe laser spectroscopy. 21,[27][28][29][30][31][32][33] The different isomers of the solvated aromatic cluster can easily be distinguished by their unique S 1 -S 0 UV transition energy. Then, a solvated cluster with a specific conformation can selectively be ionized by the REMPI process via S 1 using two-color two-photon (UV-UV') ionization with adjustable ionization excess energy.…”