Decay Dynamics in Molecular Beams

Abstract

The phenomenon of power law decays in molecular beams is reviewed. The transition from a canonical to a microcanonical description of the decay is analyzed, and the appearance of the power law decay derived. Deviations from a power law often contain information on parallel competing processes. This is illustrated with examples where thermal radiation or dark unimolecular channels are the competing processes. Also corrections to the power law due to finite heat capacities and from nonideal energy distributions are derived. Finally, the consequences for the interpretation of action spectroscopy data are reviewed.

Defining the Temperature of an Isolated Molecule

“…We could think of a setup where a small, isolated molecular ion is photoexcited in an electrostatic ion trap. 4,6,35 The laser pulse duration should be such as it allows thermal equilibration before radiative decay starts, but without losing too much energy resolution.…”

Defining the temperature of an isolated molecule

“…We could think of a setup where a small, isolated molecular ion is photoexcited in an electrostatic ion trap. 4,6,38 The laser pulse duration should be such as it allows thermal equilibration before radiative decay starts but without losing too much energy resolution. Then, monitoring its radiative cooling would inform on its peak temperature (before any cooling).…”

“…Indeed, the temperature of isolated molecules and small finite systems has been under scrutiny for decades in diverse fields. It is needed for computing unimolecular reaction rates, [2][3][4] sampling initial conditions for dynamics, 5 studying fragmentation and radiative cooling of electrostatically trapped ions, [6][7][8] determining thermionic electron emission of clusters beams, 9 characterizing phase transitions in clusters, 10 or assigning molecular species in the interstellar medium. [11][12][13] Defining such a temperature may be helpful even for understanding the photophysics of chromophores in vacuum-like hydrophobic cavities of proteins.…”

Defining the Temperature of an Isolated Molecule

“…We could think of a setup where a small, isolated molecular ion is photoexcited in an electrostatic ion trap. 4,6,33 The laser pulse duration should be such as it allows thermal equilibration before radiative decay starts, but without losing too much energy resolution.…”

“…It is needed for computing unimolecular reaction rates, [2][3][4] sampling initial conditions for dynamics, 5 studying fragmentation and radiative cooling of electrostatically trapped ions, [6][7][8] determining thermionic electron emission of clusters beams, 9 characterizing phase transitions in clusters, 10 or assigning molecular species in the interstellar medium. [11][12][13] Indeed, defining such a temperature may be helpful even for understanding the photophysics of chromophores in vacuumlike hydrophobic cavities of proteins.…”