Intramolecular vibrational redistribution: from high-resolution spectra to real-time dynamics

Abstract

Intramolecular vibrational redistribution is a fundamental phenomenon observed in polyatomic molecules when sufficiently excited vibrationally. In this paper, results mostly from the last two decades of research on this subject are summarized, obtained either from infrared spectroscopy with a resolution of as high as 10 À4 cm ÀI or, in a different approach, by using various pump-probe schemes with a temporal resolution from dozens of picoseconds to subpicoseconds.A A Makarov, A L Malinovsky, E A Ryabov

Electron attachment to some naphthoquinone derivatives: long‐lived molecular anion formation

“…In the case of electron capture in a higher‐lying MO (shape resonance), the anion formed can relax into its electronic ground state through a single or a series of ultrafast intramolecular electron transitions . These radiationless transitions typically take place in a timescale comparable with that of vibrational relaxation (~10 –13 s) . As a result, the total anion vibrational excitation energy (E – ) is equal to the sum of the EA a and initial vibrational energy (E m ) of the target neutral molecule, plus the kinetic energy ( ε ) of the incident electron.…”

“…The simplest relationship between the detachment time of the anion state and other parameters of the system is an Arrhenius approximation: where k a = τ 0 –1 is the autodetachment rate constant, ω 0 is the typical anion vibrational frequency ( τ 0 is the vibration relaxation time), k is the Boltzmann constant, Tˉ is the anion effective temperature . Therefore, accurate measurements of anion lifetimes should allow us to evaluate the EA a of the target molecule.…”

“…In the same way we can evaluate E m = NkT , where T is the temperature of the target molecule (ionization chamber temperature). Assuming that the pre‐exponent factor ω 0 /2π is equal to the inverse of the intramolecular vibrational energy redistribution (IVR) time ( τ 0 ) of the anion, then Eqn. may be written as: …”

Coherent and stochastic contributions of compound resonances in atomic processes: Electron recombination, photoionization, and scattering

“…Well-known examples of quantum-chaotic systems are excited heavy nuclei (e.g., those formed by neutron capture) [2,3], and heavy atoms and ions with open f shells, such as Ce or Au 24+ [4][5][6]. Another example is given by the vibrational motion of polyatomic molecules where anharmonic mixing between normal modes leads to intramolecular vibrational redistribution (IVR) [7][8][9][10]. Chaotic resonances have also been found recently in ultracold collisions of erbium atoms [11] (a manifestation of chaotic states in the excited Er 2 molecule).…”

“…To make Eqs. (10) and (15) [or (16) and (17)] more accurate for application to real systems, one can diagonalize the Hamiltonian matrix in the subspace of the doorway states. This should supply more accurate energies E d and amplitudes involving the doorways.…”