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Zillich, Robert E.; Kwon, Yongkyung; Whaley, K. Birgitta

doi:10.1103/physrevlett.93.250401

Cited by 62 publications

(51 citation statements)

References 14 publications

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“…The IR transition to the J 1:5 state is found to be homogeneously broadened. We attribute both observations to the coupling between the molecular rotation and phonon/roton excitations in superfluid 4 He droplets. Spectroscopy of molecules in He nanodroplets is a very promising technique for investigating chemical reactions at ultralow temperatures.…”

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confidence: 79%

High-Resolution Spectroscopy of NO in Helium Droplets: A Prototype for Open Shell Molecular Interactions in a Quantum Solvent

Haeften

Metzelthin²,

Rudolph³

et al. 2005

Phys. Rev. Lett.

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We have measured the high-resolution infrared spectrum of the radical NO in the 2 1=2 state in superfluid helium nanodroplets. The features are attributed to the -doubling splitting and the hyperfine structure. The hyperfine interaction is found to be unaffected by the He solvation. For the -doubling splitting, we find a considerable increase by 55% compared to the gas phase. This is explained by a confinement of the electronically excited NO states by the surrounding He. The rotational level spacing is decreased to 76% of the gas phase value. The IR transition to the J 1:5 state is found to be homogeneously broadened. We attribute both observations to the coupling between the molecular rotation and phonon/roton excitations in superfluid 4 He droplets. DOI: 10.1103/PhysRevLett.95.215301 PACS numbers: 67.40.Fd, 33.15.Pw, 33.20.Ea, 33.20.Wr Spectroscopy of molecules in He nanodroplets is a very promising technique for investigating chemical reactions at ultralow temperatures. In such reactions, radicals play an important role [1]. It is, therefore, of interest to probe the influence of the He environment on a radical. While at present quite a number of closed shell molecules have been studied in He droplets [2], only little is known about the influence of the helium droplets on the spectra [3] and the electronic structure of radicals. The infrared spectra of many radicals exhibit hyperfine splitting and -type doubling. These effects are well known in the gas phase but have never been studied in solvents.In this Letter, we report the measurement of the IR spectrum of NO in He droplets. NO is an open shell molecule and has a 2 1=2 electronic ground state. The rotational levels of NO show hyperfine structure and -type doubling. While the hyperfine splitting reflects the magnetic interaction, -type doubling arises from rotational interaction of the ground state with higher electronic states. The coupling to the higher electronic or ÿ states splits the degenerate energy levels of the 2 1=2ground state. We will show that the droplets increase the magnitude of the -type doubling and discuss the implications for the electronically excited states of NO within the He solvent. The lower rotational energy levels of NO lie in the interesting region of the collective excitations of superfluid He. In particular, they are close to the roton excitations. NO is therefore a good candidate to investigate the role of these excitations in the rotational energy relaxation or in the shift of the rotational levels, as recently pointed out by theory [4,5]. For this purpose, NO as a diatomic molecule is ideal because it has only a single vibrational mode. The vibrational energy is much larger than the collective excitations of liquid He (1875 cm ÿ1 10 cm ÿ1 ). Therefore, vibrational relaxation is extremely slow.The experiments have been carried out using a new apparatus at Bochum. The setup is similar to that used by Hartmann et al. and explained in detail elsewhere [5,6]. Here we give only a brief description. Helium is expanded at 40 ...

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confidence: 79%

High-Resolution Spectroscopy of NO in Helium Droplets: A Prototype for Open Shell Molecular Interactions in a Quantum Solvent

Haeften

Metzelthin²,

Rudolph³

et al. 2005

Phys. Rev. Lett.

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“…Blinov and Roy [149,150] have introduced similar calculations using PIMC instead of DMC to calculate the orientational correlation functions. The Whaley group is also using similar methods [151,152] in addition to several others that they have pioneered.…”

Section: Superfluidity and Molecular Rotation In Nanodropletsmentioning

confidence: 99%

“…Zillich and Whaley have developed the DMC/CBF method for treating the interaction of molecular rotation excitation with the phonons and rotons of helium and applied it to the case of HCN [153] and C 2 H 2 [151], an important yet challenging problem. This model treats the phonons of the droplet as if they are continuous and have the same form as for bulk helium and then decomposes the density anisotropy that rotates with the molecule in terms of these phonon modes.…”

Section: Superfluidity and Molecular Rotation In Nanodropletsmentioning

confidence: 99%

Spectroscopy and dynamics in helium nanodroplets

Stienkemeier

Lehmann

2006

J. Phys. B: At. Mol. Opt. Phys.

396

555

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Abstract. This article provides a review of recent work in the field of helium nanodroplet spectroscopy with emphasis on the dynamical aspects of the interactions between molecules in helium as well as their interaction with this unique quantum solvent. Emphasis is placed on experimental methods and studies introducing recent new approaches, in particular including time-resolved techniques. Corresponding theoretical results on the energetics and dynamics of helium droplets are also discussed.

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“…The coupling of rotations to a bath has been extensively studied in the context of molecules in helium nanodroplets using density functional calculations [63], a combination of semi-analytical and Monte Carlo techniques [64,65], reptation quantum Monte Carlo [66][67][68][69], path integral Monte Carlo [70][71][72][73][74][75][76], and diffusion Monte Carlo [75,[77][78][79][80][81][82][83][84]. All these techniques, however, model the environment as a cluster of a finite size, and -as a consequence -are computationally expensive.…”

Section: Introductionmentioning

confidence: 99%

Diagrammatic approach to orbital quantum impurities interacting with a many-particle environment

Bighin

Lemeshko

2017

Phys. Rev. B

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Recently it was shown that an impurity exchanging orbital angular momentum with a surrounding bath can be described in terms of the angulon quasiparticle [Phys. Rev. Lett. 118, 095301 (2017)]. The angulon consists of a quantum rotor dressed by a many-particle field of boson excitations, and can be formed out of, for example, a molecule or a nonspherical atom in superfluid helium, or out of an electron coupled to lattice phonons or a Bose condensate. Here we develop an approach to the angulon based on the path-integral formalism, which sets the ground for a systematic, perturbative treatment of the angulon problem. The resulting perturbation series can be interpreted in terms of Feynman diagrams, from which, in turn, one can derive a set of diagrammatic rules. These rules extend the machinery of the graphical theory of angular momentum -well known from theoretical atomic spectroscopy -to the case where an environment with an infinite number of degrees of freedom is present. In particular, we show that each diagram can be interpreted as a 'skeleton,' which enforces angular momentum conservation, dressed by an additional many-body contribution. This connection between the angulon theory and the graphical theory of angular momentum is particularly important as it allows to systematically and substantially simplify the analytical representation of each diagram. In order to exemplify the technique, we calculate the 1− and 2−loop contributions to the angulon self-energy, the spectral function, and the quasiparticle weight. The diagrammatic theory we develop paves the way to investigate next-to-leading order quantities in a more compact way compared to the variational approaches.

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Roton-Rotation Coupling of Acetylene inH4e

Cited by 62 publications

References 14 publications

High-Resolution Spectroscopy of NO in Helium Droplets: A Prototype for Open Shell Molecular Interactions in a Quantum Solvent

High-Resolution Spectroscopy of NO in Helium Droplets: A Prototype for Open Shell Molecular Interactions in a Quantum Solvent

Spectroscopy and dynamics in helium nanodroplets

Diagrammatic approach to orbital quantum impurities interacting with a many-particle environment

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