Multiple‐Photon Infrared Laser Photophysics and Photochemistry. I

Abstract

This paper begins our review paper on the multiple-photon excitation of molecules by intense infrared laser light. The whole review will be given in installments. In this first part we bring forward certain general concepts on spectroscopy, molecular physics and chemical kinetics essential for understanding the later material.

Vibrational spectra of discrete UO22+ halide complexes in the gas phase

“…When the laser frequency matches that of a normal vibrational mode of the gas-phase ion, energy is absorbed and subsequently distributed throughout the ion by intramolecular vibrational redistribution (IVR). The rapidity of the IVR process allows the energy of each photon to be "relaxed" prior to the absorption of the next, and thus allows promotion of the ion's internal energy to the dissociation threshold by multiple photon absorption [25]. Prior studies have shown that the infrared spectra obtained using the IRMPD method presented here are comparable to those obtained using linear absorption techniques [27,36,38].…”

“…In general, infrared spectra of the uranyl complex ions were collected by monitoring the efficiency of IRMPD as a function of photon energy [25]. In this experiment, isolated complexes were irradiated using two FELIX macropulses (40 mJ per macropulse, 5 s pulse duration, FWHM bandwidth around 0.5% of central ).…”

“…In the mid-IR region of the spectrum, photons are not sufficiently energetic to cause dissociation needed to observe vibrational fundamentals. However the FEL can deliver sufficient pulse energies so that complexes will absorb multiple photons, and are energized to their dissociation threshold [25]. This approach has been used to examine the IR spectra of a number of metal coordination complexes [13,[26][27][28][29][30][31], and has been applied to uranyl coordination complexes in several studies by our group, specifically [UO 2 (solvent) n ] 2+ [32], [UO 2 (solvent)] + [33], [UO 2 (anion)(solvent)] + [34], and [UO 2 (anion) 3 ] − complexes [35,36].…”

Anharmonic Effect on Unimolecular Reactions with Application to the Photodissociation of Ethylene

“…The anharmonic force field calculations have been carried out. 6 The need for anharmonic correction to existing reaction rate theories has been emphasized by several authors, [7][8][9] and Troe 10 proposed a simple empirical method for generating anharmonic vibrational densities of states using experimental thermodynamic data.…”

Anharmonic Effect of the Unimolecular Dissociation of HFCO and DFCO

“…Several authors have concentrated on the requirement for the anharmonic correction to previous reaction rate theories. [21][22][23] For this reason, using experimental thermodynamic data, J. Troe 24 presented a simple empirical method for generating anharmonic vibrational densitiy of states. In 2007, a method which can carry out the first principle calculations about the rate constants of molecular reactions within the framework of the transition state theory has been proposed by Yao and Lin (YL).…”