Nuclear wave-packet dynamics on nearly degenerate two adiabatic potential energy surfaces in the excited state of KIFcenters

Abstract

Nuclear wave-packet dynamics in the excited state of KI F centers is investigated by using time-resolved luminescence spectroscopy based on the up-conversion technique. The observed transient spectrum involves an oscillatory and a nonoscillatory component. The origins of these components are interrogated by comparing the results with a model calculation based on the resonant secondary radiation theory. The oscillatory part reflects the coupling of the 2s-like electron mainly to the totally symmetric local mode around the F center. The nonoscillatory part reflects the incoherent population of the vibrational levels in the 2p-like state, which couples to many bulk phonon modes with a broad density of state. The model calculation suggests that the transition probability to the 2p-like state is approximately 0.05.

Observation of nuclear wave packets in the excited state of the F-center in alkali halides

“…The former was employed for KBr and KI measurements, while the latter for KCl and RbCl measurements. Details of the former measurement system are displayed in the previous paper [5]. In this paper, the latter system is briefly explained by referring to Fig.…”

“…In this work, we review our recent studies on the dynamics of the nuclear wave packet (NWP) at the F-center in four alkali halides, potassium chloride (KCl) [1], potassium bromide (KBr) [2,3], potassium iodide (KI) [4,5], and rubidium chloride (RbCl) [1]. Especially, the observation of the dominant modes of the oscillations of the nuclear wave packets is demonstrated.…”

Excitation and Time‐Evolution of Coherent Optical Phonons

“…For example, strong exciton-phonon coupling was demonstrated for lead phthalocyanine [69] and CuI [70] as an intense enhancement of the coherent phonon amplitude at the excitonic resonances. In alkali halides [71], nuclear wave packets localized near F centers were observed as periodic modulations of the luminescence spectra.…”

Second2s−2plevel crossing at theFcenter in KCl evidenced by frequency upconversion spectroscopy

“…As a prototype of a strongly coupled localized electron-phonon system, the NWP dynamics has been demonstrated in real time by femtosecond laser spectroscopy. [8][9][10][11][12][13] The ground state is the 1s state and the first excited state is composed of the 2s and 2p states. A configuration coordinate diagram is drawn in Fig.…”