Superfluid Effects in Doped Helium Clusters: A Quantum Chemistry Perspective

1. Spin solvent effects in doped helium clusters: A microscopic manifestation of superfluidityCritical stability, Erice, Oct. 2008 Pablo Villarreal IFF (CSIC), Madrid-SPAIN p.villarreal@imaff.cfmac.csic.es

2. OUTLINE • Diatomic Perturbed by Surrounding He atoms: Quantum Chemistry Approach • Infra-Red & Raman Spectral Simulations • Some results & prospective lines

3. Experimental Set-up

5. Quantum chemistry approach electrons  He atoms nuclei  impurity Firstly proposed by P. Jungwirth & A. KrylovJ. Chem. Phys. 115 (2001) 10214 3He2-Rg, -SF6 (triplet)

7. VHeN-BC= • FULL PES:

9. ADIABATIC APPROACH To be solved, at each r bond-length, by Hartree or Hartree-Fock procedures

10. neglecting Coriolis couplings

11. Schrödinger Eq. for the distorted molecule: Total wave function:

27. OCS, Toennies et al., Phys. Today 54,31 (2001) Br2, López-Durán et al., PRL 93, 53401 (2004)

31. Boson scenario: Selection Rules:

32. Fermion scenario: Qbranchesappear too ! In addition toPandRbranches,

33. Stick spectrum For linear polarized incident light, and considering a Boltzmann distribution of rotational states at a given temperature T, a line of intensity should appear at a frequency of the photon

36. (4He)18-ICl (3He)18-ICl

37. 4He 3He OCS in He nanodroplets ICl---(He)N, N→∞

38. Summary & Outlook Using a Quantum Chemistry approach, we have simulated the spectra of simple impurities within He clusters The treatment rests on an accurate ab initio description of the electronic PES The main features experimentally found are qualitatively described in this framework, although… …more accurate treatments are highly desired, and a careful analysis of the validity of the model (light dopants) should be performed After that, the procedure could be applied to a wide range of many-body problems, from Particle Physics to Condensed Matter…

39. PROSPECTIVE LINES

41. N=4, 3-g

43. Raman spectrum isotropic component polarizability anisotropic “

44. “exact”: QC : QC : selection rule P and R branches forbidden “exact”: propensity rule position?? intensity ??

45. at T = 0.5 K

46. S(0) :

47. !!

49. U. La Sapienza (ROMA) ARGONNE Nat. Lab. CSIC (MADRID) U. BORDEAUX