Figure 1

(a) Pump-probe scheme. Part of the laser beam after the beam splitter (BS) is shaped in a pulse shaper with a computer-controlled spatial light modulator (SLM). The probe ionization pulses at 400 nm are obtained by second-harmonic generation in a BBO crystal by the unshaped fundamental pulses. The angular momentum in the excited state is determined as a function of time delay between the excitation and ionization pulses. (b) Schematic layout of the experiment. The angular momentum in the 5$p$ state is probed via ultrafast photoionization, using velocity map imaging. R, E, and G are the repeller, extractor, and ground plates respectively. (c) The excitation and the probe level scheme. (d) The experimental calibration PADs, obtained during the excitation with circularly and linearly polarized pulses, resulting in $\langle L_z\rangle$ $=$ 1 (only $m_L$ $=$ −1 level populated), 0 (both $m_L$ $=$ −1 and $m_L$ $=$ 1 levels are populated), and −1 ($m_L$ $=$ 1 level is populated), respectively. The laser beam propagates in the vertical direction.Reuse & Permissions

Figure 2

(a) Temporal evolution of pulse field helicity $\vec{h}=i[\vec{E}\times {\vec{E}}^{*}]$ for the cases when the polarization step is applied at ${\lambda }_{ig}$ $+$ 0.25 nm (black solid line) and at ${\lambda }_{ig}$ $+$ 1.25 nm (blue dashed line). The inset shows the excitation spectrum. Part of the spectrum above 784 nm is blocked. (b) Experimental and calculated populations of the $m$ $=$ 1, $m$ $=$ −1 sublevels as a function of time. Polarization step ${\lambda }_{\mathrm{step}}$ is applied at ${\lambda }_{ig}$+ 0.25 nm. (c) The same as the data shown in (b) but for the case when the polarization step is applied at ${\lambda }_{ig}$+1.25 nm.Reuse & Permissions

Figure 3

Experimental and calculated product of population and expectation value $\left(\right|a_1{|}_{}^2+|a_{-1}{|}_{}^2)〈L_z〉$ as a function of the polarization step position for conditions as in Fig. 2.Reuse & Permissions

Figure 4

Ultrafast evolution of angular momentum during off-resonant excitation. The excitation spectrum is continuous from 780.7 nm to 784 nm. The polarization step is applied at 782.5 nm. (a) Temporal evolution of the pulse field helicity $\vec{h}=i[\vec{E}\times {\vec{E}}^{*}]$ for the pulses having only the polarization step (black solid line) and the polarization step together with π/2 phase step at 782.5 nm (blue dashed line). (b) Experimental and calculated product of population and expectation value $\left(\right|a_1{|}_{}^2+|a_{-1}{|}_{}^2)〈L_z〉$ for the pulse containing polarization step only. (c) The same as the data in (b) but for the case when the spectrum has both polarization step and π/2 phase step at 782.5 nm.Reuse & Permissions