Ion-Pair Formation in n-Butyl Bromide through 5p Ryberg State Predissociation

Lauren F. Heald, Colleen L. Loftus, Robert S. Gosman, Scott G. Sayres

Research output: Contribution to journalArticlepeer-review


The ultrafast photodynamics of n-butyl bromide are explored with femtosecond time-resolved mass spectrometry. Absorption of two UV (400 nm) pump photons induces the direct dissociation of the C-Br bond from the A state within 160 fs. Absorption of three UV pump photons excites the molecule into the 5p Rydberg state which undergoes several relaxation pathways including to the ion-pair state. Relaxation to the ion-pair state is tracked through the transient of the C4H9+ fragment and suggests an E state lifetime of 10.8 ± 0.5 ps, in close agreement with the tunneling time of smaller molecules. Predissociation from the 5p Rydberg states leads to the β-elimination of H-Br and formation of C4H8+ within 3.0 ± 0.25 ps. A portion of the excited parent molecule avoids the ion-pair formation and instead relaxes through the Rydberg excited state manifold into the D state within 30.2 ± 0.21 ps.

Original languageEnglish (US)
Pages (from-to)9651-9657
Number of pages7
JournalJournal of Physical Chemistry A
Issue number51
StatePublished - Dec 29 2022

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry


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