High-spectral-resolution attosecond absorption spectroscopy of autoionization in xenon

The decay of highly excited states of xenon after absorption of extreme ultraviolet light is directly tracked via attosecond transient absorption spectroscopy using a time-delayed near-infrared perturbing pulse. The lifetimes of the autoionizing 5$s$5$p^6$6$p$ and 5$s$5$p^6$7$p$ channels are determined to be (21.9 ± 1.3) fs and (48.4 ± 5.0) fs, respectively. The observed values support lifetime estimates obtained by traditional linewidth measurements. The experiment additionally obtains the temporal evolution of the decay as a function of energy detuning from the resonance center, and a quantum mechanical formalism is introduced that correctly accounts for the observed energy dependence.

Figure 1

Experimental setup for transient absorption spectroscopy in xenon. WP: wave plate, FS: fused silica plate, BBO: crystal for second-harmonic generation.

Figure 2

(a) Static XUV absorbance spectrum of the 5$s$5$p^{6}np$ autoionizing states in xenon. (b) XUV absorbance spectrum of xenon in a strong NIR laser field with an intensity of 1.3 × 10${}^{12}$ W/cm${}^2$. Negative time delays correspond to the NIR pulse arriving before the XUV pulse at the target. (c) Line-out (solid line) and fit (dashed line) of the $n$ = 6 (dark blue) and $n$ = 7 (light blue) resonances; see text for details.

Figure 3

(a) Xenon absorbance dependent on different time delays between XUV and NIR and at different energies around the xenon 5$s$5$p^6$6$p$ autoionizing resonance. 0 meV is considered the line center. (b) Corresponding simulated absorbance curves calculated with a three-state model (solid line) and with Eq. (3) (dots; see text for details).