Strongly aligned molecules inside helium droplets in the near-adiabatic regime

Abstract

Iodine (I${}_2$) molecules embedded in He nanodroplets are aligned by a 160 ps long laser pulse. The highest degree of alignment, occurring at the peak of the pulse and quantified by $⟨{\cos }^2{\theta }_{2D}⟩$, is measured as a function of the laser intensity. The results are well described by $⟨{\cos }^2{\theta }_{2D}⟩$ calculated for a gas of isolated molecules each with an effective rotational constant of 0.6 times the gas-phase value, and at a temperature of 0.4 K. Theoretical analysis using the angulon quasiparticle to describe rotating molecules in superfluid helium rationalizes why the alignment mechanism is similar to that of isolated molecules with an effective rotational constant. A major advantage of molecules in He droplets is that their 0.4 K temperature leads to stronger alignment than what can generally be achieved for gas phase molecules -- here demonstrated by a direct comparison of the droplet results to measurements on a $\sim$ 1 K supersonic beam of isolated molecules. This point is further illustrated for more complex system by measurements on 1,4-diiodobenzene and 1,4-dibromobenzene. For all three molecular species studied the highest values of $⟨{\cos }^2{\theta }_{2D}⟩$ achieved in He droplets exceed 0.96.

11 pages, 8 figures

References in corpus (9)

• Quantum-state selection, alignment, and orientation of large molecules using static electric and laser fields
• Rotation of quantum impurities in the presence of a many-body environment
• Control and femtosecond time-resolved imaging of torsion in a chiral molecule
• Quasiparticle approach to molecules interacting with quantum solvents
• Laser-induced rotation of iodine molecules in He-nanodroplets: revivals and breaking-free
• Rotation of cold molecular ions inside a Bose-Einstein condensate
• Fingerprints of angulon instabilities in the spectra of matrix-isolated molecules
• Anomalous screening of quantum impurities by a neutral environment
• Angular self-localization of impurities rotating in a bosonic bath

Cited by in corpus (17)

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• Rotational coherence spectroscopy of molecules in helium nanodroplets: Reconciling the time and the frequency domains
• Hyperfine-Structure-Induced Depolarization of Impulsively Aligned ${\mathrm{I}}_2$ Molecules
• Femtosecond rotational dynamics of D${}_2$ molecules in superfluid helium nanodroplets
• Switched Wave Packets with Spectrally Truncated Chirped Pulses
• Quantum-State-Sensitive Detection of Alkali Dimers on Helium Nanodroplets by Laser-Induced Coulomb Explosion
• Fingerprints of angulon instabilities in the spectra of matrix-isolated molecules
• Laser-induced Coulomb Explosion Imaging of Alkali Dimers on Helium Nanodroplets
• Laser-induced Coulomb explosion imaging of \ce{(C6H5Br)2} and \ce{C6H5Br-I2} dimers in helium nanodroplets using the Timepix3
• Excited rotational states of molecules in a superfluid
• Alignment of the CS${}_2$ Dimer Embedded in Helium Droplets Induced by a Circularly Polarized Laser Pulse
• Intermolecular forces and correlations mediated by a phonon bath
• Prospects of nuclear-coupled-dark-matter detection via correlation spectroscopy of I${}_2^{+}$ and Ca${}^{+}$
• Attractive and repulsive angulons in superfluid environments