TY - JOUR

T1 - Dipole-quadrupole interference spectroscopy

T2 - Observation of an autoionizing He 1D Rydberg series

AU - Krässig, B.

AU - Kanter, E. P.

AU - Southworth, S. H.

AU - Young, L.

AU - Wehlitz, R.

AU - Deharak, B. A.

AU - Martin, N. L.S.

PY - 2012/11/12

Y1 - 2012/11/12

N2 - We have used dipole-quadrupole interference spectroscopy to observe an optically forbidden quadrupole Rydberg series of helium autoionizing levels. The technique measures the forward-backward asymmetry of photoelectron angular distributions produced in the vacuum ultraviolet photoionization of helium. The resonant behavior of this asymmetry in the region of a quadrupole autoionizing level enables the determination of the position, width, and Fano line-profile parameter q of the level. We have obtained these quantities for the He 2(1,0)n+1D Rydberg series for n=2-7. We find that for n≤3 all three quantities have the expected n scaling, with a quantum defect of 0.31. For n≤3 the average q parameter lies close to zero, whereas for n=2 it is negative.

AB - We have used dipole-quadrupole interference spectroscopy to observe an optically forbidden quadrupole Rydberg series of helium autoionizing levels. The technique measures the forward-backward asymmetry of photoelectron angular distributions produced in the vacuum ultraviolet photoionization of helium. The resonant behavior of this asymmetry in the region of a quadrupole autoionizing level enables the determination of the position, width, and Fano line-profile parameter q of the level. We have obtained these quantities for the He 2(1,0)n+1D Rydberg series for n=2-7. We find that for n≤3 all three quantities have the expected n scaling, with a quantum defect of 0.31. For n≤3 the average q parameter lies close to zero, whereas for n=2 it is negative.

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U2 - 10.1103/PhysRevA.86.053408

DO - 10.1103/PhysRevA.86.053408

M3 - Article

AN - SCOPUS:84869074705

SN - 1050-2947

VL - 86

JO - Physical Review A - Atomic, Molecular, and Optical Physics

JF - Physical Review A - Atomic, Molecular, and Optical Physics

IS - 5

M1 - 053408

ER -