Issue 32, 2016

A 1 + 1′ resonance-enhanced multiphoton ionization scheme for rotationally state-selective detection of formaldehyde via the à 1A2[X with combining tilde]1A1 transition

Abstract

The formaldehyde molecule is an important model system for understanding dynamical processes in small polyatomic molecules. However, prior to this work, there have been no reports of a resonance-enhanced multiphoton ionization (REMPI) detection scheme for formaldehyde suitable for rovibrationally state-selective detection in molecular beam scattering experiments. Previously reported tunable REMPI schemes are either non-rotationally resolved, involve multiple resonant steps, or involve many-photon ionization steps. In the current work, we present a new 1 + 1′ REMPI scheme for formaldehyde. The first photon is tunable and provides rotational resolution via the vibronically allowed à 1A2[X with combining tilde] 1A1 transition. Molecules are then directly ionized from the à state by one photon of 157 nm. The results indicate that the ionization cross section from the 41 vibrational level of the à state is independent of the rotational level used as intermediate, to within experimental uncertainty. The 1 + 1′ REMPI intensities are therefore directly proportional to the à ← [X with combining tilde] absorption intensities and can be used for quantitative measurement of [X with combining tilde]-state population distributions.

Graphical abstract: A 1 + 1′ resonance-enhanced multiphoton ionization scheme for rotationally state-selective detection of formaldehyde via the à 1A2 ←  [[X with combining tilde]]  1A1 transition

Supplementary files

Article information

Article type
Paper
Submitted
02 Jun 2016
Accepted
19 Jul 2016
First published
20 Jul 2016
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2016,18, 22355-22363

A 1 + 1′ resonance-enhanced multiphoton ionization scheme for rotationally state-selective detection of formaldehyde via the à 1A2[X with combining tilde] 1A1 transition

G. B. Park, B. C. Krüger, S. Meyer, A. M. Wodtke and T. Schäfer, Phys. Chem. Chem. Phys., 2016, 18, 22355 DOI: 10.1039/C6CP03833F

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