Figure 1

Schematic overview of the experimental arrangement. The skimmed supersonic beam propagates in the $-z$ direction halfway between two metallic electrodes consisting of a plane parallel segment followed by a region in which the surface makes an angle of 45° with the atomic beam. The VUV laser beam propagates parallel to the plate surfaces and perpendicular to the atomic beam. Photoexcitation is carried out in either homogeneous (point $A$) or inhomogeneous (point $B$) electric fields. The solid lines represent lines of constant electric fields ranging from $3V/2{\mathrm{c}\mathrm{m}}^{-1}$ (top line) to $V/5{\mathrm{c}\mathrm{m}}^{-1}$ (bottom line) in steps of $V/10{\mathrm{c}\mathrm{m}}^{-1}$.Reuse & Permissions

Figure 2

Stark map of the $n=22$, $M_J=0$ argon Rydberg states. The origin of the intensity scale of each spectrum corresponds to the electric field strength in $\mathrm{V}/\mathrm{c}\mathrm{m}$, from bottom to top 0, 70, 136, 204, 272, $340\mathrm{V}/\mathrm{c}\mathrm{m}$. The linear high $\ell$ Stark manifold is situated between the dotted lines. The states labeled $a$, $a^{\prime }$, $b$, $b^{\prime }$, $c$, $c^{\prime }$, and $d$ correspond to the $22d[1/2{]}_1$, $23d[1/2{]}_1$, $22d[3/2{]}_1$, $24s[3/2{]}_1$, $23p[1/2{]}_0$, $24p[1/2{]}_0$, and $24p[5/2{]}_2$ states, respectively. The upper panel shows the fine structure of three red Stark states with $k=19$, 17, and 15, from left to right, where $k$ represents a hydrogenic label determined using Eq. (1).Reuse & Permissions

Figure 3

Stark map of the avoided crossing of the $24p[1/2{]}_0$ state with the high $\ell$ manifold. Traces pointing upward (downward) were measured in homogeneous (inhomogeneous) fields. The dashed lines show interpolations between measurements.Reuse & Permissions

Figure 4

TOF of the $24p[1/2{]}_0$ (solid line) and the $n=22$, $k=21$ Stark state (dashed line) below (upper panel) and above (lower panel) the avoided crossing. The labels $X$, $Y$, $X^{\prime }$, and $Y^{\prime }$ refer to the spectral positions marked in Fig. 3.Reuse & Permissions

Figure 5

Lower panel: Spectrum of the energy region where the $n=24$ and $n=25$ manifold meet. The dashed lines show the behavior of the three outer groups of Stark states in the $n=24$ manifold and the two outer groups of Stark states in the $n=25$ manifold. Upper panel: The TOF traces of state $a$ (left trace), state $b$ (right trace), and a zero-field state.Reuse & Permissions

Figure 6

Decay of the $n=25$ $k=16$ Stark state excited in a field of $200\mathrm{V}/\mathrm{c}\mathrm{m}$.Reuse & Permissions