Multi-photon UV photolysis of naphthalene–gas mixtures: A new oscillatory system

Abstract

A new closed gas-phase system with complex oscillatory behaviour is reported. Employing the pulsed cavity ring-down technique, the absorption of static naphthalene vapour buffered with a noble gas at room temperature was measured as a function of time at 650 nm after UV multi-photon laser photolysis at 308 nm. The absorption dynamics of the static (unstirred) system exhibits extraordinary periodic and complex oscillations with periods ranging from seconds to many minutes, persisting for up to 4 h. Depending on the buffer gas pressure, several types of dynamical responses can be generated.

Incoherent broad-band cavity-enhanced absorption spectroscopy

“…However, the majority of such "exotic phenomena" are observed either in the condensed phase [Epstein98,Field85], in gas flow reactors or combustion reactions [Scott90,Scott94]. The serendipitous discovery of a new closed gas phase system was reported by Ruth et al [Ruth02b] exhibiting unusual periodic and complex dynamical behaviour. The original objective was to test whether UV multi-photon ionization (MPI) is a viable way to selectively create a sufficient concentration of polycyclic aromatic hydrocarbon (PAH) cations in a supersonic expansion, for absorption measurements of long wavelength π − π transitions, using the sensitive cavity ring-down (CRD) technique [O' Keefe88,Wheeler98].…”

“…The phenomenon was found at preliminary experiments by accident and was first investigated by CRDS [Ruth02b,Gash04] at one wavelength only. In this work first IBBCEA spectra of the oscillating absorption are presented as a function of time.…”

“…These unexpected observations made us revise our original objectives and led to the investigation of this new nonlinear gas phase phenomenon [Ruth02b]. A detailed description of these experiments varying different parameters of the setup and using CRDS to detect the absorption is given in [Gash04].…”

“…To explain the oscillation phenomenon to the reader, the CRD setup used first and a short overview of the CRD results is given below (refer also [Ruth02b] and [Gash04]), followed then by the presentation and discussion of new experimental data measured with IBBCEAS.…”

Diamond-like-carbon nanoparticle production and agglomeration following UV multi-photon excitation of static naphthalene/helium gas mixtures

“…The experimental setup has been described in detail elsewhere, 29,30 and will only be briefly outlined here. The sample gas mixture is contained in a static gas chamber (volume ∼5.3 dm 3 ), which can be evacuated to 10 −3 mbar.…”