1
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Briant M, Mestdagh JM, Gaveau MA, Poisson L. Reaction dynamics within a cluster environment. Phys Chem Chem Phys 2022; 24:9807-9835. [PMID: 35441619 DOI: 10.1039/d1cp05783a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This perspective article reviews experimental and theoretical works where rare gas clusters and helium nanodroplets are used as a nanoreactor to investigate chemical dynamics in a solvent environment. A historical perspective is presented first followed by specific considerations on the mobility of reactants within these reaction media. The dynamical response of pure clusters and nanodroplets to photoexcitation is shortly reviewed before examining the role of the cluster (or nanodroplet) degrees of freedom in the photodynamics of the guest atoms and molecules.
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Affiliation(s)
- Marc Briant
- Université Paris-Saclay, CEA, CNRS, LIDYL, 91191, Gif-sur-Yvette, France
| | | | - Marc-André Gaveau
- Université Paris-Saclay, CEA, CNRS, LIDYL, 91191, Gif-sur-Yvette, France
| | - Lionel Poisson
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405, Orsay, France.
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2
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García-Alfonso E, Coppens F, Barranco M, Pi M, Stienkemeier F, Halberstadt N. Alkali atoms attached to vortex-hosting helium nanodroplets. J Chem Phys 2020; 152:194109. [PMID: 33687233 DOI: 10.1063/5.0008923] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Light absorption or fluorescence excitation spectroscopy of alkali atoms attached to 4He droplets is investigated as a possible way for detecting the presence of vortices. To this end, we have calculated the equilibrium configuration and energetics of alkali atoms attached to a 4He1000 droplet hosting a vortex line using 4He density functional theory. We use them to study how the dipole absorption spectrum of the alkali atom is modified when the impurity is attached to a vortex line. Spectra are found to be blue-shifted (higher frequencies) and broadened compared to vortex-free droplets because the dimple in which the alkali atom sits at the intersection of the vortex line and the droplet surface is deeper. This effect is smaller for lighter alkali atoms and all the more so when using a quantum description since, in this case, they sit further away from the droplet surface on average due to their zero-point motion. Spectral modifications due to the presence of a vortex line are minor for np ← ns excitation and therefore insufficient for vortex detection. In the case of higher n'p ← ns or n's ← ns (n' > n) excitations, the shifts are larger as the excited state orbital is more extended and therefore more sensitive to changes in the surrounding helium density.
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Affiliation(s)
| | - Francois Coppens
- Université Toulouse 3 and CNRS, Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, 118 route de Narbonne, F-31062 Toulouse Cedex 09, France
| | - Manuel Barranco
- Université Toulouse 3 and CNRS, Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, 118 route de Narbonne, F-31062 Toulouse Cedex 09, France
| | - Martí Pi
- Departament FQA, Facultat de Física, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| | | | - Nadine Halberstadt
- Université Toulouse 3 and CNRS, Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, 118 route de Narbonne, F-31062 Toulouse Cedex 09, France
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3
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Lackner F, Ernst WE. Photoinduced Molecule Formation of Spatially Separated Atoms on Helium Nanodroplets. J Phys Chem Lett 2018; 9:3561-3566. [PMID: 29893573 DOI: 10.1021/acs.jpclett.8b01530] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Besides the use as cold matrix for spectroscopic studies, superfluid helium droplets have served as a cold environment for the synthesis of molecules and clusters. Since vibrational frequencies of molecules in helium droplets exhibit almost no shift compared to the free molecule values, one could assume the solvated particles move frictionless and undergo a reaction as soon as their paths cross. There have been a few unexplained observations that seemed to indicate cases of two species on one droplet not forming bonds but remaining isolated. In this work, we performed a systematic study of helium droplets doped with one rubidium and one strontium atom showing that besides a reaction to RbSr, there is a probability of finding separated Rb and Sr atoms on one droplet that only react after electronic excitation. Our results further indicate that ground-state Sr atoms can reside at the surface as well as inside the droplet.
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Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria, European Union
| | - Wolfgang E Ernst
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria, European Union
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4
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Lackner F, Krois G, Ernst WE. Lithium atoms on helium nanodroplets: Rydberg series and ionization dynamics. J Chem Phys 2018; 147:184302. [PMID: 29141430 DOI: 10.1063/1.5004543] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The electronic excitation spectrum of lithium atoms residing on the surface of helium nanodroplets is presented and analyzed employing a Rydberg-Ritz approach. Utilizing resonant two-photon ionization spectroscopy, two different Rydberg series have been identified: one assigned to the nS(Σ) series and the other with predominantly nP(Π) character. For high Rydberg states, which have been resolved up to n = 13, the surrounding helium effectively screens the valence electron from the Li ion core, as indicated by the apparent red-shift of Li transitions and lowered quantum defects on the droplet with respect to their free atom counterparts. For low n states, the screening effect is weakened and the prevailing repulsive interaction gives rise to strongly broadened and blue-shifted transitions. The red-shifts originate from the polarization of nearby He atoms by the positive Li ion core. As a consequence of this effect, the ionization threshold is lowered by 116 ± 10 cm-1 for Li on helium droplets with a radius of about 40 Å. Upon single-photon ionization, heavy complexes corresponding to Li ions attached to intact helium droplets are detected. We conclude that ionization close to the on-droplet ionization threshold triggers a dynamic process in which the Li ion core undergoes a transition from a surface site into the droplet.
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Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Günter Krois
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
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5
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Ben Hadj Ayed M, Hamdi R, Ghalla H, Oujia B, Gadéa FX. Theoretical investigation of the electronic properties of alkali atoms interacting with helium rare gas using a pseudopotential approach. Theor Chem Acc 2018. [DOI: 10.1007/s00214-018-2266-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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6
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Vindel Zandbergen P, Barranco M, Cargnoni F, Drabbels M, Pi M, Halberstadt N. Helium-induced electronic transitions in photo-excited Ba+–Hen exciplexes. J Chem Phys 2018; 148:144302. [DOI: 10.1063/1.5022863] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Patricia Vindel Zandbergen
- Laboratoire Collisions Agrégats Réactivité (LCAR), IRSAMC, Université de Toulouse, CNRS UMR 5589, Toulouse, France
| | - Manuel Barranco
- Laboratoire Collisions Agrégats Réactivité (LCAR), IRSAMC, Université de Toulouse, CNRS UMR 5589, Toulouse, France
- Departament FQA, Facultat de Física, Universitat de Barcelona, Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
| | | | - Marcel Drabbels
- Laboratory of Molecular Nanodynamics, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Martí Pi
- Departament FQA, Facultat de Física, Universitat de Barcelona, Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
| | - Nadine Halberstadt
- Laboratoire Collisions Agrégats Réactivité (LCAR), IRSAMC, Université de Toulouse, CNRS UMR 5589, Toulouse, France
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7
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Ancilotto F, Barranco M, Coppens F, Eloranta J, Halberstadt N, Hernando A, Mateo D, Pi M. Density functional theory of doped superfluid liquid helium and nanodroplets. INT REV PHYS CHEM 2017. [DOI: 10.1080/0144235x.2017.1351672] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Francesco Ancilotto
- Dipartimento di Fisica e Astronomia ‘Galileo Galilei’ and CNISM, Università di Padova, Padova, Italy
- CNR-IOM Democritos, Trieste, Italy
| | - Manuel Barranco
- Facultat de Física, Departament FQA, Universitat de Barcelona, Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - François Coppens
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - Jussi Eloranta
- Department of Chemistry and Biochemistry, California State University at Northridge, Northridge, CA, USA
| | - Nadine Halberstadt
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - Alberto Hernando
- Social Thermodynamics Applied Research (SThAR), EPFL Innovation Park, Lausanne, Switzerland
| | - David Mateo
- Applied Complexity Group, Singapore University of Technology and Design, Singapore, Singapore
| | - Martí Pi
- Facultat de Física, Departament FQA, Universitat de Barcelona, Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
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8
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Pototschnig JV, Lackner F, Hauser AW, Ernst WE. Rydberg states of alkali atoms on superfluid helium nanodroplets: inside or outside? Phys Chem Chem Phys 2017; 19:14718-14728. [PMID: 28540939 PMCID: PMC5708348 DOI: 10.1039/c7cp02332d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 05/12/2017] [Indexed: 11/28/2022]
Abstract
Electronic excitations of an electron bound to an alkali metal ion inside a droplet of superfluid 4He are computed via a combination of helium density functional theory and the numerical integration of the Schrödinger equation for a single electron in a modified, He density dependent atomic pseudopotential. The application of a spectral method to the radial part of the valence electron wavefunction allows the computation of highly excited Rydberg states. For low principal quantum numbers, the energy required to push the electron outward is larger than the solvation energy of the ion. However, for higher principal quantum numbers the situation is reversed, which suggests the stability of a system where the ion sits inside the droplet while the valence electron orbits the nanodroplet.
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Affiliation(s)
- Johann V. Pototschnig
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Florian Lackner
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Andreas W. Hauser
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Wolfgang E. Ernst
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
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9
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Sieg A, von Vangerow J, Stienkemeier F, Dulieu O, Mudrich M. Desorption Dynamics of Rb 2 Molecules Off the Surface of Helium Nanodroplets. J Phys Chem A 2016; 120:7641-7649. [PMID: 27606714 DOI: 10.1021/acs.jpca.6b05732] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The desorption dynamics of rubidium dimers (Rb2) off the surface of helium nanodroplets induced by laser excitation is studied by employing both nanosecond and femtosecond ion imaging spectroscopy. Similarly to alkali metal atoms, we find that the Rb2 desorption process resembles the dissociation of a diatomic molecule. However, both angular and energy distributions of detected Rb2+ ions appear to be most crucially determined by the Rb2 intramolecular degrees of freedom rather than by those of the Rb2HeN complex. The pump-probe dynamics of Rb2+ is found to be slower than that of Rb+, pointing at a weaker effective guest-host repulsion for excited molecules than for single atoms.
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Affiliation(s)
- A Sieg
- Physikalisches Institut, Universität Freiburg , 79104 Freiburg, Germany
| | - J von Vangerow
- Physikalisches Institut, Universität Freiburg , 79104 Freiburg, Germany
| | - F Stienkemeier
- Physikalisches Institut, Universität Freiburg , 79104 Freiburg, Germany
| | - O Dulieu
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS Cachan, Université Paris-Saclay , 91405 Orsay Cedex, France
| | - M Mudrich
- Physikalisches Institut, Universität Freiburg , 79104 Freiburg, Germany
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10
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Ziemkiewicz MP, Neumark DM, Gessner O. Ultrafast electronic dynamics in helium nanodroplets. INT REV PHYS CHEM 2015. [DOI: 10.1080/0144235x.2015.1051353] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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11
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Pototschnig JV, Krois G, Lackner F, Ernst WE. Investigation of the RbCa molecule: Experiment and theory. JOURNAL OF MOLECULAR SPECTROSCOPY 2015; 310:126-134. [PMID: 25922550 PMCID: PMC4407902 DOI: 10.1016/j.jms.2015.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 01/12/2015] [Indexed: 06/04/2023]
Abstract
We present a thorough theoretical and experimental study of the electronic structure of RbCa. The mixed alkali-alkaline earth molecule RbCa was formed on superfluid helium nanodroplets. Excited states of the molecule in the range of 13 000-23 000 cm-1 were recorded by resonance enhanced multi-photon ionization time-of-flight spectroscopy. The experiment is accompanied by high level ab initio calculations of ground and excited state properties, utilizing a multireference configuration interaction method based on multiconfigurational self consistent field calculations. With this approach the potential energy curves and permanent electric dipole moments of 24 electronic states were calculated. In addition we computed the transition dipole moments for transitions from the ground into excited states. The combination of experiment and theory allowed the assignment of features in the recorded spectrum to the excited [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] states, where the experiment allowed to benchmark the calculation. This is the first experimental work giving insight into the previously unknown RbCa molecule, which offers great prospects in ultracold molecular physics due to its magnetic and electronic dipole moment in the [Formula: see text] ground state.
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12
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Lackner F, Krois G, Buchsteiner T, Pototschnig JV, Ernst WE. Helium-droplet-assisted preparation of cold RbSr molecules. PHYSICAL REVIEW LETTERS 2014; 113:153001. [PMID: 25375707 DOI: 10.1103/physrevlett.113.153001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Indexed: 06/04/2023]
Abstract
We present a combined experimental and theoretical study of the RbSr molecule. The experimental approach is based on the formation of RbSr molecules on helium nanodroplets. Utilizing two-photon ionization spectroscopy, an excitation spectrum ranging from 11,600 up to 23,000 cm(-1) was recorded. High level ab initio calculations of potential energy curves and transition dipole moments accompany the experiment and facilitate an assignment of transitions. We show that RbSr molecules desorb from the helium droplets upon excitation, which enables dispersed fluorescence spectroscopy of free RbSr. These spectra elucidate X(2)Σ(+) ground and excited state properties. Emission spectra originating from states corresponding to the Rb(5s(2)S) + Sr(5s5p(3)P) asymptote were recorded; spin-orbit coupling was included for the simulation. The results should provide a good basis for achieving the formation of this molecule in cold collisions, thus offering intriguing prospects for ultracold molecular physics.
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Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
| | - Günter Krois
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
| | - Thomas Buchsteiner
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
| | - Johann V Pototschnig
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
| | - Wolfgang E Ernst
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria
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13
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Koch M, Kautsch A, Lackner F, Ernst WE. One- and two-color resonant photoionization spectroscopy of chromium-doped helium nanodroplets. J Phys Chem A 2014; 118:8373-9. [PMID: 24708058 PMCID: PMC4166682 DOI: 10.1021/jp501285r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
We investigate the photoinduced relaxation
dynamics of Cr atoms
embedded into superfluid helium nanodroplets. One- and two-color resonant
two-photon ionization (1CR2PI and 2CR2PI, respectively) are applied
to study the two strong ground state transitions z7P2,3,4° ←
a7S3 and y7P2,3,4° ← a7S3. Upon photoexcitation, Cr* atoms are ejected from the
droplet in various excited states, as well as paired with helium atoms
as Cr*–Hen exciplexes. For the
y7P2,3,4° intermediate state, comparison of the two methods reveals
that energetically lower states than previously identified are also
populated. With 1CR2PI we find that the population of ejected z5P3° states is reduced for increasing droplet size, indicating that population
is transferred preferentially to lower states during longer interaction
with the droplet. In the 2CR2PI spectra we find evidence for generation
of bare Cr atoms in their septet ground state (a7S3) and metastable quintet state (a5S2), which we attribute to a photoinduced fast excitation–relaxation
cycle mediated by the droplet. A fraction of Cr atoms in these ground
and metastable states is attached to helium atoms, as indicated by
blue wings next to bare atom spectral lines. These relaxation channels
provide new insight into the interaction of excited transition metal
atoms with helium nanodroplets.
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Affiliation(s)
- Markus Koch
- Institute of Experimental Physics, Graz University of Technology , Petersgasse 16, A-8010 Graz, Austria
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14
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Krois G, Lackner F, Pototschnig JV, Buchsteiner T, Ernst WE. Characterization of RbSr molecules: spectral analysis on helium droplets. Phys Chem Chem Phys 2014; 16:22373-81. [DOI: 10.1039/c4cp03135k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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16
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von Vangerow J, Sieg A, Stienkemeier F, Mudrich M, Leal A, Mateo D, Hernando A, Barranco M, Pi M. Desorption Dynamics of Heavy Alkali Metal Atoms (Rb, Cs) Off the Surface of Helium Nanodroplets. J Phys Chem A 2014; 118:6604-14. [DOI: 10.1021/jp503308w] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- J. von Vangerow
- Physikalisches
Institut, Universität Freiburg, 79104 Freiburg, Germany
| | - A. Sieg
- Physikalisches
Institut, Universität Freiburg, 79104 Freiburg, Germany
| | - F. Stienkemeier
- Physikalisches
Institut, Universität Freiburg, 79104 Freiburg, Germany
| | - M. Mudrich
- Physikalisches
Institut, Universität Freiburg, 79104 Freiburg, Germany
| | - A. Leal
- Departament
ECM, Facultat de Física and IN2UB, Universitat de Barcelona, 08028 Barcelona, Spain
| | - D. Mateo
- Departament
ECM, Facultat de Física and IN2UB, Universitat de Barcelona, 08028 Barcelona, Spain
- Department
of Chemistry and Biochemistry, California State University at Northridge, 18111 Nordhoff Street, Northridge, California 91330, United States
| | - A. Hernando
- Laboratoire
de Chimie Physique Moléculaire, Swiss Federal Institute of Technology Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - M. Barranco
- Departament
ECM, Facultat de Física and IN2UB, Universitat de Barcelona, 08028 Barcelona, Spain
| | - M. Pi
- Departament
ECM, Facultat de Física and IN2UB, Universitat de Barcelona, 08028 Barcelona, Spain
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17
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Lindebner F, Kautsch A, Koch M, Ernst WE. Laser ionization and spectroscopy of Cu in superfluid helium nanodroplets. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2014; 365-366:255-259. [PMID: 25844053 PMCID: PMC4376070 DOI: 10.1016/j.ijms.2013.12.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 12/18/2013] [Accepted: 12/19/2013] [Indexed: 06/04/2023]
Abstract
Mass and optical spectroscopic methods are used for the analysis of copper (Cu) atoms and clusters doped to helium nanodroplets (HeN). A two-color resonant two-photon ionization scheme is applied to study the Cu 2P[Formula: see text]S1/2 ground state transition. The absorption is strongly broadened for Cu atoms submerged inside helium nanodroplets and a comparison with computed literature values is provided. An observed ejection of the dopant from the droplet is triggered upon excitation, populating energetically lower states. The formation of Cu n clusters up to Cu7 inside helium nanodroplets was observed by means of electron impact ionization mass spectroscopy.
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18
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Loginov E, Drabbels M. Dynamics of Excited Sodium Atoms Attached to Helium Nanodroplets. J Phys Chem A 2014; 118:2738-48. [DOI: 10.1021/jp4121996] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Evgeniy Loginov
- Laboratoire de Chimie Physique
Moléculaire, Ecole polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Marcel Drabbels
- Laboratoire de Chimie Physique
Moléculaire, Ecole polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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19
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Krois G, Pototschnig JV, Lackner F, Ernst WE. Spectroscopy of cold LiCa molecules formed on helium nanodroplets. J Phys Chem A 2013; 117:13719-31. [PMID: 24028555 PMCID: PMC3871282 DOI: 10.1021/jp407818k] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 09/11/2013] [Indexed: 11/30/2022]
Abstract
We report on the formation of mixed alkali-alkaline earth molecules (LiCa) on helium nanodroplets and present a comprehensive experimental and theoretical study of the ground and excited states of LiCa. Resonance enhanced multiphoton ionization time-of-flight (REMPI-TOF) spectroscopy and laser induced fluorescence (LIF) spectroscopy were used for the experimental investigation of LiCa from 15000 to 25500 cm(-1). The 4(2)Σ(+) and 3(2)Π states show a vibrational structure accompanied by distinct phonon wings, which allows us to determine molecular parameters as well as to study the interaction of the molecule with the helium droplet. Higher excited states (4(2)Π, 5(2)Σ(+), 5(2)Π, and 6(2)Σ(+)) are not vibrationally resolved and vibronic transitions start to overlap. The experimental spectrum is well reproduced by high-level ab initio calculations. By using a multireference configuration interaction (MRCI) approach, we calculated the 19 lowest lying potential energy curves (PECs) of the LiCa molecule. On the basis of these calculations, we could identify previously unobserved transitions. Our results demonstrate that the helium droplet isolation approach is a powerful method for the characterization of tailor-made alkali-alkaline earth molecules. In this way, important contributions can be made to the search for optimal pathways toward the creation of ultracold alkali-alkaline earth ground state molecules from the corresponding atomic species. Furthermore, a test for PECs calculated by ab initio methods is provided.
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Affiliation(s)
- Günter Krois
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Johann V. Pototschnig
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Wolfgang E. Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
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20
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Hernando A, Beswick JA, Halberstadt N. Communication: Angular momentum alignment and fluorescence polarization of alkali atoms photodetached from helium nanodroplets. J Chem Phys 2013; 139:221102. [DOI: 10.1063/1.4843235] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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21
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Lackner F, Poms J, Krois G, Pototschnig JV, Ernst WE. Spectroscopy of lithium atoms and molecules on helium nanodroplets. J Phys Chem A 2013; 117:11866-73. [PMID: 23895106 PMCID: PMC3839407 DOI: 10.1021/jp4030238] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
We
report on the spectroscopic investigation of lithium atoms and
lithium dimers in their triplet manifold on the surface of helium
nanodroplets (HeN). We present the excitation spectrum
of the 3p ← 2s and 3d ← 2s two-photon transitions for
single Li atoms on HeN. The atoms are excited from the
2S(Σ) ground state into Δ, Π, and Σ pseudodiatomic
molecular substates. Excitation spectra are recorded by resonance
enhanced multiphoton ionization time-of-flight (REMPI-TOF) mass spectroscopy,
which allows an investigation of the exciplex (Li*–Hem, m = 1–3) formation process
in the Li–HeN system. Electronic states are shifted
and broadened with respect to free atom states, which is explained
within the pseudodiatomic model. The assignment is assisted by theoretical
calculations, which are based on the Orsay–Trento density functional
where the interaction between the helium droplet and the lithium atom
is introduced by a pairwise additive approach. When a droplet is doped
with more than one alkali atom, the fragility of the alkali–HeN systems leads preferably to the formation of high-spin molecules
on the droplets. We use this property of helium nanodroplets for the
preparation of Li dimers in their triplet ground state (13Σu+).
The excitation spectrum of the 23Πg(ν′
= 0–11) ← 13Σu+(ν″ = 0) transition is presented.
The interaction between the molecule and the droplet manifests in
a broadening of the transitions with a characteristic asymmetric form.
The broadening extends to the blue side of each vibronic level, which
is caused by the simultaneous excitation of the molecule and vibrations
of the droplet (phonons). The two isotopes of Li form 6Li2 and 7Li2 as well as isotope
mixed 6Li7Li molecules on the droplet surface.
By using REMPI-TOF mass spectroscopy, isotope-dependent effects could
be studied.
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Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics, Graz University of Technology , Petersgasse 16, A-8010 Graz, Austria/EU
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22
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Lackner F, Krois G, Ernst WE. Rydberg–Ritz analysis and quantum defects for Rb and Cs atoms on helium nanodroplets. Mol Phys 2013. [DOI: 10.1080/00268976.2013.788792] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics, Graz University of Technology , Graz, Austria
| | - Günter Krois
- Institute of Experimental Physics, Graz University of Technology , Graz, Austria
| | - Wolfgang E. Ernst
- Institute of Experimental Physics, Graz University of Technology , Graz, Austria
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23
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Zhang X, Drabbels M. Communication: Barium ions and helium nanodroplets: Solvation and desolvation. J Chem Phys 2012; 137:051102. [DOI: 10.1063/1.4743900] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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24
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Lackner F, Krois G, Koch M, Ernst WE. Rubidium on Helium Droplets: Analysis of an Exotic Rydberg Complex for n* < 20 and 0 ≤ l ≤ 3. J Phys Chem Lett 2012; 3:1404-1408. [PMID: 26286790 DOI: 10.1021/jz300381y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Rubidium atom Rydberg states perturbed by helium droplets of different sizes provide insight into the role of a nanosized dielectric on the Coulomb potential. The observation of droplet size-dependent shifts of excited states with respect to bare atom states is explained by a decreased quantum defect and a lowered ionization threshold. Within the scope of a Rydberg model, we demonstrate that quantum defects and ionization potentials are constant for each specific Rydberg series, which confirms the Rydberg character of excited Rubidium states on helium droplets. A set of six Rydberg series could be identified. Individual Rydberg states are observed with effective principal quantum numbers up to n* ≈ 19 and l ≤ 3, for which the expectation value of the electron orbital radius is about 10 times larger than the droplet radius.
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Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU
| | - Günter Krois
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU
| | - Markus Koch
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU
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25
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Loginov E, Drabbels M. Spectroscopy and dynamics of barium-doped helium nanodroplets. J Chem Phys 2012; 136:154302. [PMID: 22519321 DOI: 10.1063/1.3701565] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Evgeniy Loginov
- Laboratoire de Chimie Physique Moléculaire, Swiss Federal Institute of Technology Lausanne, CH-1015 Lausanne, Switzerland
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26
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Fechner L, Grüner B, Sieg A, Callegari C, Ancilotto F, Stienkemeier F, Mudrich M. Photoionization and imaging spectroscopy of rubidium atoms attached to helium nanodroplets. Phys Chem Chem Phys 2012; 14:3843-51. [PMID: 22327348 DOI: 10.1039/c2cp22749e] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- L Fechner
- Physikalisches Institut, Universität Freiburg, Freiburg, Germany
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