Microsolvation of phthalocyanine molecules in superfluid helium nanodroplets as revealed by the optical line shape at electronic origin

Fuchs, Stefan; Fischer, Johannes; Slenczka, Alkwin; Karra, Mallikarjun; Friedrich, Břetislav

doi:10.1063/1.5022006

Cited by 7 publications

(6 citation statements)

References 21 publications

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“…The attachment of polar water molecule(s) to the bare Pc molecule appears to have little effect−other than a shift in the transition energies. As we have shown in more detail for bare Pc and porphine, 26,27 the asymmetry in these line shapes is helium-induced and reflects the inhomogeneity caused by the droplet size distribution. The perseverance of the line shape despite the attachment of a water molecule supports the idea of an effect that is caused by the droplet volume rather than just the helium solvation layer surrounding the dopant cluster.…”

Section: Discussionmentioning

confidence: 61%

“…The line shapes of all three Pc–H 2 O clusters (top and middle panel in Figure ) show a similar asymmetry as recorded for bare Pc (bottom panel in Figure ) in helium droplets. As discussed in detail in refs , , and , this asymmetry can be quantitatively explained by inhomogeneous line broadening due to the log-normal size distribution of the helium droplets as present in the helium droplet beam. Apparently, the attachment of a single water molecule to Pc does not significantly alter the helium-induced fine structure.…”

Section: Results and Discussionmentioning

confidence: 90%

“…For larger droplets, the rotational fine structure is obscured by pronounced line broadening . Recent investigations of the ZPL at the electronic origin of phthalocyanine and porphine led to the conclusion that inhomogeneous line broadening due to the droplet size distribution is responsible for the asymmetric line shape found. , Simulations of the line shape by means of the excluded volume model developed for molecules embedded in a polarizable environment suffice to reproduce the experimental line shape without including particular spectral features of the rotational band system. , Apparently, molecular rotation is readily resolved in helium droplets when coupled to vibrational excitation. , However, upon coupling to electronic excitation, helium-induced perturbations mask spectral contributions expected for a free rotation of the dopant species.…”

Section: Introductionmentioning

confidence: 99%

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Heterogeneous Clusters of Phthalocyanine and Water Prepared and Probed in Superfluid Helium Nanodroplets

et al. 2019

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Superfluid helium nanodroplets comprised of thousands to millions of helium atoms can serve as a reactor for the synthesis of heterogeneous molecular clusters at cryogenic conditions. The cluster synthesis occurs via consecutive pick-up of the cluster building blocks by the helium droplet and their subsequent coalescence within the droplet. The effective collision cross section of the building blocks is determined by the helium droplet size and thus exceeds by orders of magnitude that of a reactive collision in the gas phase. Moreover, the cryogenic helium environment (at 0.38 K) as a host promotes the formation of metastable cluster configurations. The question arises as to the extent of the actual involvement of the helium environment in the cluster formation. The present study deals with clusters of single phthalocyanine (Pc) molecules with single water molecules. A large fluorophore such as Pc offers several sites where the water molecule can attach. The resulting isomeric variants of the Pc−H 2 O complex can be selectively identified by electronic spectroscopy. We compare the experimental electronic spectra of the Pc− H 2 O complex generated in superfluid helium nanodroplets with the results of quantum-chemical calculations on the same cluster but under gas-phase conditions. The number of isomeric variants observed in the helium droplet experiment comes out the same as that obtained from our gas-phase calculations.

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Section: Discussionmentioning

confidence: 61%

Section: Results and Discussionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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Heterogeneous Clusters of Phthalocyanine and Water Prepared and Probed in Superfluid Helium Nanodroplets

et al. 2019

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“…In order to solve the problem of microsolvation and to understand the influence of the helium droplet on its guest molecule, the spectral shapes of the ZPL and PW have to be deciphered. In addition to numerous such studies for various dopant species, which are most detailed for tetracene (TC) − and phthalocyanine (Pc), ,,,− systematic investigations of a series of derivatives of certain dopant species such as pyrromethene dyes, , porphyrine, ,, and anthracene ,,− have been reported. For some of these studies, the corresponding gas phase spectra were also measured for comparison.…”

Section: Introductionmentioning

confidence: 99%

Anthracene–Argon Clusters Generated in Superfluid Helium Nanodroplets: New Aspects on Cluster Formation and Microsolvation

Lottner

Slenczka

2019

J. Phys. Chem. A

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About two decades after extensive studies on anthracene−Ar n clusters in the gas phase, we report corresponding studies in superfluid helium droplets. With AN as a small fluorophore and spectroscopic data from the gas phase and helium droplets, both the formation of clusters and the microsolvation in superfluid helium droplets can be studied. As expected for helium droplets, a significantly higher number of isomeric variants of the respective cluster sizes are obtained, because metastable variants are stabilized by the low temperature and the surrounding helium. Moreover, spectroscopic data recorded in helium droplets reveal cluster configurations with Ar atoms shielded by a helium solvation layer. Surprisingly, AN−Ar n clusters with more than four Ar atoms do not appear to form rigid configurations. The helium droplet data in combination with the gas phase spectra may serve as a suitable reference for further theoretical investigations on solvation and cluster formation in superfluid helium droplets.

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“…In the case of phthalocyanine accessing the bulk-limit requires droplet sizes of at least 10 6 helium atoms generated upon supercritical expansion conditions. Experimental results for the ZPL line shape reveal vanishing of the asymmetry upon approaching the transition from subcritical to supercritical expansion conditions in the helium droplet source [33,34,36]. Far beyond this limit a very sharp double peak structure is resolved (cf.…”

Section: Phthalocyanine In Superfluid Helium Dropletsmentioning

confidence: 97%

Electronic Spectroscopy in Superfluid Helium Droplets

Schlaghaufer

Fischer

Slenczka

2022

Topics in Applied Physics

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Electronic spectroscopy has been instrumental in demonstrating the properties of helium droplets as a cryogenic matrix for molecules. The electronic spectrum of glyoxal, which was one of the first molecules investigated in helium droplets by means of electronic spectroscopy, showed two features that provided convincing evidence that the droplets were superfluid. These were free rotation and the distinct shape of the phonon side band which could be directly assigned to the characteristic dispersion curve of a superfluid. On closer examination, however, details such as increased moments of inertia and a spectral response on the droplet size distribution revealed unexpected features of microsolvation in the superfluid helium. In the course of studying many different molecules, it has become clear that electronic spectroscopy in helium droplets provides insight into the detailed effects of microsolvation. These in turn lead to numerous questions regarding the interaction with the superfluid which are discussed in this chapter. In addition, the influence of microsolvation in helium droplets on van der Waals clusters generated inside helium droplets are discussed. Finally, the effect of helium solvation on unimolecular or bimolecular elementary chemical reactions is evaluated in comparison with corresponding experiments in the gas phase. Particular focus of this article lies on the spectral features related to helium solvation which are not yet fully understood.

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Microsolvation of phthalocyanine molecules in superfluid helium nanodroplets as revealed by the optical line shape at electronic origin

Cited by 7 publications

References 21 publications

Heterogeneous Clusters of Phthalocyanine and Water Prepared and Probed in Superfluid Helium Nanodroplets

Heterogeneous Clusters of Phthalocyanine and Water Prepared and Probed in Superfluid Helium Nanodroplets

Anthracene–Argon Clusters Generated in Superfluid Helium Nanodroplets: New Aspects on Cluster Formation and Microsolvation

Electronic Spectroscopy in Superfluid Helium Droplets

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