Lineshape of rotational spectrum of CO in He4 droplets

Zillich, Robert E.; Whaley, K. Birgitta; Haeften, K. von

doi:10.1063/1.2833979

Cited by 13 publications

(7 citation statements)

References 41 publications

(76 reference statements)

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“…Previous experiments on microwave spectroscopy of molecules in helium droplets have shown a broadening of the molecular rotational lines, which amounts to ∼ 100 MHz in the case of OCS [2]. The line shapes are attributed to inhomogeneous broadening, and at least for CO in helium this was confirmed by calculations [50]. In order to account for this effect, we introduce a Gaussian broadening of B eff values with a standard deviation γ = 0.05 B eff , which corresponds to half width at half maximum of 66 MHz for I 2 .…”

Section: Dynamics Of I2 In Heliummentioning

confidence: 51%

Laser-Induced Rotation of Iodine Molecules in Helium Nanodroplets: Revivals and Breaking Free

et al. 2017

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Rotation of molecules embedded in He nanodroplets is explored by a combination of fs laserinduced alignment experiments and angulon quasiparticle theory. We demonstrate that at low fluence of the fs alignment pulse, the molecule and its solvation shell can be set into coherent collective rotation lasting long enough to form revivals. With increasing fluence, however, the revivals disappear -instead, rotational dynamics as rapid as for an isolated molecule is observed during the first few picoseconds. Classical calculations trace this phenomenon to transient decoupling of the molecule from its He shell. Our results open novel opportunities for studying non-equilibrium solute-solvent dynamics and quantum thermalization.

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Section: Dynamics Of I2 In Heliummentioning

confidence: 51%

Laser-Induced Rotation of Iodine Molecules in Helium Nanodroplets: Revivals and Breaking Free

et al. 2017

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“…[33] This interpretation is supported by theoretical work using path integral methods. [32,75,76] Experiments on charged atoms or molecules solvated in helium are, so far, limited to mass spectra; they cannot provide a similar level of detail. Is the observation of steps in the ion yield inconsistent with superfluidity in the first solvation shell?…”

Section: Discussionmentioning

confidence: 99%

On the Size of Ions Solvated in Helium Clusters

Silva

Waldburger

Jaksch

et al. 2009

Chemistry A European J

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Helium nanodroplets are doped with SF(6), C(4)F(8), CCl(4), C(6)H(5)Br, CH(3)I, and I(2). Upon interaction with free electrons a variety of positively and negatively charged cluster ions X(+/-)He(n) are observed where X(+/-) = F(+/-), Cl(+/-), Br(+/-), I(+), I(2) (+), or CH(3)I(+). The yield of these ions versus cluster size n drops at characteristic sizes n(s) that range from n(s) = 10.2+/-0.6 for F(+) to n(s) = 22.2+/-0.2 for Br(-). n(s) values for halide anions are about 70% larger than for the corresponding cations. The steps in the ion yield suggest closure of the first solvation shell. We propose a simple classical model to estimate ionic radii from n(s). Assuming the helium density in the first solvation shell equals the helium bulk density one finds that radii of halide anions in helium are nearly twice as large as in alkali halide crystals, indicating the formation of an anion bubble due to the repulsive forces that derive from the exchange interaction. In spite of the simplicity of our model, anion radii derived from it agree within approximately 10% with values derived from the mobility of halide anions in superfluid bulk helium, and with values computed by quantum Monte Carlo methods for X(-)He(n) cluster anions.

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“…It is important to note that the angulon quasiparticle theory described below is substantially simpler -and therefore more transparent -than numerical calculations based on Monte-Carlo algorithms [52,[54][55][56][57][58][69][70][71][72][73][74][75][76][77][78][79].…”

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confidence: 99%

Fingerprints of angulon instabilities in the spectra of matrix-isolated molecules

Cherepanov

Lemeshko

2017

Phys. Rev. Materials

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The formation of vortices is usually considered to be the main mechanism of angular momentum disposal in superfluids. Recently, it was predicted that a superfluid can acquire angular momentum via an alternative, microscopic route -namely, through interaction with rotating impurities, forming so-called 'angulon quasiparticles ' [Phys. Rev. Lett. 114, 203001 (2015)]. The angulon instabilities correspond to transfer of a small number of angular momentum quanta from the impurity to the superfluid, as opposed to vortex instabilities, where angular momentum is quantized in units of per atom. Furthermore, since conventional impurities (such as molecules) represent three-dimensional (3D) rotors, the angular momentum transferred is intrinsically 3D as well, as opposed to a merely planar rotation which is inherent to vortices. Herein we show that the angulon theory can explain the anomalous broadening of the spectroscopic lines observed for CH3 and NH3 molecules in superfluid helium nanodroplets, thereby providing a fingerprint of the emerging angulon instabilities in experiment.One of the distinct features of the superfluid phase is the formation of vortices -topological defects carrying quantized angular momentum, which arise if the bulk of the superfluid rotates faster than some critical angular velocity [1,2]. Vortex nucleation has been considered to be the main mechanism angular momentum disposal in superfluids [1][2][3][4][5]. Recently, it was predicted that a superfluid can acquire angular momentum via a different, microscopic route, which takes effect in the presence of rotating impurities, such as molecules [6][7][8][9][10][11][12][13]. In particular, it was demonstrated that a rotating impurity immersed in a superfluid forms the 'angulon' quasiparticle, which can be thought of as a rigid rotor dressed by a cloud of superfluid excitations carrying angular momentum [14-21].The angulon theory was able to describe, in good agreement with experiment, renormalization of rotational constants [22,23] and laser-induced dynamics [24,25] of molecules in superfluid helium nanodroplets. One of the key predictions of the angulon theory are the socalled 'angulon instabilities ' [14-16] that occur at some critical value of the molecule-superfluid coupling where the angulon quasiparticle becomes unstable and one or a few quanta of angular momentum are resonantly transferred from the impurity to the superfluid. These instabilities are fundamentally different from the vortex instabilities, associated with the transfer of angular momentum quantised in units of per atom of the superfluid. Furthermore, vortices can be thought of as planar rotors, i.e., the eigenstates of theL z operator. Angulons, on the other hand, are the eigenstates of the total angular momentum operator,L 2 , and therefore the transferred angular momentum is three-dimensional. While vortex instabilities have been subject to several experimental studies in the context of superfluid helium [4,5,[26][27][28][29][30][31], ultracold quantum gases [32][33][34][35][36]...

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Lineshape of rotational spectrum of CO in He4 droplets

Cited by 13 publications

References 41 publications

Laser-Induced Rotation of Iodine Molecules in Helium Nanodroplets: Revivals and Breaking Free

Laser-Induced Rotation of Iodine Molecules in Helium Nanodroplets: Revivals and Breaking Free

On the Size of Ions Solvated in Helium Clusters

Fingerprints of angulon instabilities in the spectra of matrix-isolated molecules

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