Ultrafast Dynamics in Na-Doped Water Clusters and the Solvated Electron

Abstract

The lifetimes of the first electronically excited state of (H(2)O)(n)...Na and (D(2)O)(n)...Na clusters up to n = 40 have been measured by two-color pump-probe spectroscopy (800 and 400 nm) with 35 fs laser pulses. The excited-state lifetime decreases rapidly from 1.2 ps at n = 2 to approximately 100 fs at n > or = 10. For (D(2)O)(n)...Na, the average lifetime is about 3.6 times longer. The fast energy redistribution is explained by conversion of the electronic excitation into vibrations of the ground state. A simple model based on Fermi's Golden Rule predicts the observed trends but fails to reproduce the observed lifetimes quantitatively. The longer lifetimes for deuterated clusters are discussed in the framework of the famous energy gap law and indicate that the stretching modes of water play an important role in the energy-transfer process.

Ultrafast photo-excitation dynamics in isolated, neutral water clusters

“…33 Briefly, a continuous supersonic molecular beam of water clusters is generated by coexpanding water vapor and helium gas from an oven through a conical nozzle into vacuum. We optimize the formation of small undoped neutral water clusters by applying partial pressures of 0.2 and 1.8 bar for water and helium, respectively.…”

Lifetimes and energetics of the first electronically excited states of NaH2O from time-resolved photoelectron imaging

“…Similar to ref. [10], we used a bi-exponential function with a short and a long relaxation time τ 1 and τ 2 , respectively, to describe the decay of the electron signal:…”

“…The interest sodium-doped water clusters (Na(H 2 O) n )) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and anion water clusters ((H 2 O) n -) [16][17][18][19][20][21][22] have attracted is attributed to their role as prototype systems for clarifying the mechanism of the emergence of the hydrated electron [23,24]. The dynamics of electronically excited states of the hydrated electron has received special attention in the context of electron initiated chemical processes and radiation damage of biological matter [7,[9][10][11]19,[25][26][27][28][29]. Schulz and coworkers have studied the lifetimes of Na(H 2 O) n for n = 2-40 after excitation from the ground state to the lowest lying electronically excited "p-states" ("s → p" transition) with pump-probe ion and electron spectroscopy [10,11].…”

“…The dynamics of electronically excited states of the hydrated electron has received special attention in the context of electron initiated chemical processes and radiation damage of biological matter [7,[9][10][11]19,[25][26][27][28][29]. Schulz and coworkers have studied the lifetimes of Na(H 2 O) n for n = 2-40 after excitation from the ground state to the lowest lying electronically excited "p-states" ("s → p" transition) with pump-probe ion and electron spectroscopy [10,11]. For simplicity we use here the nomenclature of the corresponding states and transitions in the Na atom.…”

Photoionization of small sodium-doped acetic acid clusters

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][19][20][21], and references therein), with only a few exceptions. 1-21 and references therein).…”