Superatom spin-state dynamics of structurally precise metal monolayer-protected clusters (MPCs)

Lenzi J. Williams, Patrick J. Herbert, Marcus A. Tofanelli, Christopher J. Ackerson, Kenneth Knappenberger

Research output: Contribution to journalArticle

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Abstract

Electronic spin-state dynamics were studied for a series of Au 25 (SC 8 H 9 ) 18 q and Au 24 Pd(SC 8 H 9 ) 18 monolayer-protected clusters (MPCs) prepared in a series of oxidation states, q, including q = -1, 0, +1. These clusters were chosen for study because Au 25 (SC 8 H 9 ) 18 -1 is a closed-shell superatomic cluster, but Au 25 (SC 8 H 9 ) 18 0 is an open-shell (7-electron) system; Au 25 (SC 8 H 9 ) 18 +1 and PdAu 24 (SC 8 H 9 ) 18 0 are isoelectronic (6-electron) closed-shell systems. Carrier dynamics for electronic fine structure spin states were isolated using femtosecond time-resolved circularly polarized transient-absorption spectroscopy (fs-CPTA). Excitation energies of 1.82 eV and 1.97 eV were chosen for these measurements on Au 25 (SC 8 H 9 ) 18 0 in order to achieve resonance matching with electronic fine structure transitions within the superatomic P- and D-orbital manifolds; 1.82-eV excited an unpaired P z electron to D states, whereas 1.97-eV was resonant with transitions between filled P x and P y subshells and higher-energy D orbitals. fs-CPTA measurements revealed multiple spin-polarized transient signals for neutral (open shell) Au 25 (SC 8 H 9 ) 18 , following 1.82-eV excitation, which persisted for several picoseconds; time constants of 5.03 ± 0.38 ps and 2.36 ± 0.59 ps were measured using 2.43 and 2.14 eV probes, respectively. Polarization-dependent fs-CPTA measurements of PdAu 24 (SC 8 H 9 ) 18 clusters exhibit no spin-conversion dynamics, similar to the isoelectronic Au 25 (SC 8 H 9 ) 18 +1 counterpart. These observations of cluster-specific dynamics resulted from spin-polarized superatom P to D excitation, via an unpaired P z electron of the open-shell seven-electron Au 25 (SC 8 H 9 ) 18 MPC. These results suggest that MPCs may serve as structurally well-defined prototypes for understanding spin and quantum state dynamics in nanoscale metal systems.

Original languageEnglish (US)
Article number101102
JournalJournal of Chemical Physics
Volume150
Issue number10
DOIs
StatePublished - Mar 14 2019

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Monolayers
Metals
Absorption spectroscopy
Electrons
metals
absorption spectroscopy
electrons
Excitation energy
fine structure
electronics
excitation
orbitals
Polarization
time constant
Oxidation
prototypes
oxidation
energy
probes
polarization

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Williams, Lenzi J. ; Herbert, Patrick J. ; Tofanelli, Marcus A. ; Ackerson, Christopher J. ; Knappenberger, Kenneth. / Superatom spin-state dynamics of structurally precise metal monolayer-protected clusters (MPCs). In: Journal of Chemical Physics. 2019 ; Vol. 150, No. 10.
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abstract = "Electronic spin-state dynamics were studied for a series of Au 25 (SC 8 H 9 ) 18 q and Au 24 Pd(SC 8 H 9 ) 18 monolayer-protected clusters (MPCs) prepared in a series of oxidation states, q, including q = -1, 0, +1. These clusters were chosen for study because Au 25 (SC 8 H 9 ) 18 -1 is a closed-shell superatomic cluster, but Au 25 (SC 8 H 9 ) 18 0 is an open-shell (7-electron) system; Au 25 (SC 8 H 9 ) 18 +1 and PdAu 24 (SC 8 H 9 ) 18 0 are isoelectronic (6-electron) closed-shell systems. Carrier dynamics for electronic fine structure spin states were isolated using femtosecond time-resolved circularly polarized transient-absorption spectroscopy (fs-CPTA). Excitation energies of 1.82 eV and 1.97 eV were chosen for these measurements on Au 25 (SC 8 H 9 ) 18 0 in order to achieve resonance matching with electronic fine structure transitions within the superatomic P- and D-orbital manifolds; 1.82-eV excited an unpaired P z electron to D states, whereas 1.97-eV was resonant with transitions between filled P x and P y subshells and higher-energy D orbitals. fs-CPTA measurements revealed multiple spin-polarized transient signals for neutral (open shell) Au 25 (SC 8 H 9 ) 18 , following 1.82-eV excitation, which persisted for several picoseconds; time constants of 5.03 ± 0.38 ps and 2.36 ± 0.59 ps were measured using 2.43 and 2.14 eV probes, respectively. Polarization-dependent fs-CPTA measurements of PdAu 24 (SC 8 H 9 ) 18 clusters exhibit no spin-conversion dynamics, similar to the isoelectronic Au 25 (SC 8 H 9 ) 18 +1 counterpart. These observations of cluster-specific dynamics resulted from spin-polarized superatom P to D excitation, via an unpaired P z electron of the open-shell seven-electron Au 25 (SC 8 H 9 ) 18 MPC. These results suggest that MPCs may serve as structurally well-defined prototypes for understanding spin and quantum state dynamics in nanoscale metal systems.",
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Superatom spin-state dynamics of structurally precise metal monolayer-protected clusters (MPCs). / Williams, Lenzi J.; Herbert, Patrick J.; Tofanelli, Marcus A.; Ackerson, Christopher J.; Knappenberger, Kenneth.

In: Journal of Chemical Physics, Vol. 150, No. 10, 101102, 14.03.2019.

Research output: Contribution to journalArticle

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AU - Williams, Lenzi J.

AU - Herbert, Patrick J.

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AB - Electronic spin-state dynamics were studied for a series of Au 25 (SC 8 H 9 ) 18 q and Au 24 Pd(SC 8 H 9 ) 18 monolayer-protected clusters (MPCs) prepared in a series of oxidation states, q, including q = -1, 0, +1. These clusters were chosen for study because Au 25 (SC 8 H 9 ) 18 -1 is a closed-shell superatomic cluster, but Au 25 (SC 8 H 9 ) 18 0 is an open-shell (7-electron) system; Au 25 (SC 8 H 9 ) 18 +1 and PdAu 24 (SC 8 H 9 ) 18 0 are isoelectronic (6-electron) closed-shell systems. Carrier dynamics for electronic fine structure spin states were isolated using femtosecond time-resolved circularly polarized transient-absorption spectroscopy (fs-CPTA). Excitation energies of 1.82 eV and 1.97 eV were chosen for these measurements on Au 25 (SC 8 H 9 ) 18 0 in order to achieve resonance matching with electronic fine structure transitions within the superatomic P- and D-orbital manifolds; 1.82-eV excited an unpaired P z electron to D states, whereas 1.97-eV was resonant with transitions between filled P x and P y subshells and higher-energy D orbitals. fs-CPTA measurements revealed multiple spin-polarized transient signals for neutral (open shell) Au 25 (SC 8 H 9 ) 18 , following 1.82-eV excitation, which persisted for several picoseconds; time constants of 5.03 ± 0.38 ps and 2.36 ± 0.59 ps were measured using 2.43 and 2.14 eV probes, respectively. Polarization-dependent fs-CPTA measurements of PdAu 24 (SC 8 H 9 ) 18 clusters exhibit no spin-conversion dynamics, similar to the isoelectronic Au 25 (SC 8 H 9 ) 18 +1 counterpart. These observations of cluster-specific dynamics resulted from spin-polarized superatom P to D excitation, via an unpaired P z electron of the open-shell seven-electron Au 25 (SC 8 H 9 ) 18 MPC. These results suggest that MPCs may serve as structurally well-defined prototypes for understanding spin and quantum state dynamics in nanoscale metal systems.

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