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Download Free PDFElectronic state spectroscopy of acetaldehyde, CH3CHO, by high-resolution VUV photo-absorptionNigel Mason

2003, Chemical Physics Letters

https://doi.org/10.1016/S0009-2614(03)01070-4visibility

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Abstract

The high-resolution photo-absorption cross-section of CH 3 CHO has been measured using synchrotron radiation in the range 3.0-11 eV (413 nm > k > 113 nm). Electronic state assignments have been suggested for each of the observed absorption bands incorporating both valence and Rydberg transitions. Valence transitions to the singlet and triplet states are assigned. Six Rydberg series have been assigned converging to the ionisation energy limit 10.229 eV. Rydberg orbitals of each series are classified according to the magnitude of the quantum defect (d). The measured VUV crosssections are used to derive the photolysis rates of acetaldehyde in the terrestrial atmosphere.

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Key takeaways

AI

1. The absolute photo-absorption cross-section of acetaldehyde, CH3CHO, was measured between 3.0-11 eV.
2. Six Rydberg series were assigned converging to the ionization energy limit of 10.229 eV.
3. Photolysis rates of CH3CHO were calculated, showing local lifetimes of 2.5 hours near ground level to under 1 minute at 50 km.
4. Vibrational features of the 1 np x Rydberg series were observed for the first time, enhancing understanding of electronic transitions.
5. The work aims to provide definitive measurements and classifications of electronic state spectroscopy for CH3CHO.

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FAQs

AI

What does high-resolution VUV photo-absorption reveal about acetaldehyde's electronic states?add

The findings demonstrate low cross-sections below 6.0 eV and intense peaks above 6.8 eV, indicating complex electronic state transitions.

How did the researchers measure acetaldehyde’s absolute photo-absorption cross-section?add

The study utilized synchrotron radiation and the Beer-Lambert law to calculate cross-section, ensuring data accuracy within ±5%.

What are the implications of acetaldehyde's photolysis rates on atmospheric chemistry?add

Photolysis rates calculated indicate a local lifetime of around two and a half hours near ground level, reducing to less than a minute at 50 km altitude.

What unique vibrational features were identified in acetaldehyde’s 1 np x Rydberg series?add

For the first time, this study observed significant vibrational structures in the 1 np x Rydberg series, indicating complex molecular dynamics.

When and how was the origin of acetaldehyde’s (n; 3s) Rydberg state identified?add

The origin was identified in studies around 6.6 eV with resonance-enhanced multiphoton ionization, confirming transitions predominated by oxygen lone-pair electrons.

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