Bumaliya Abulimiti

Photoelectron spectroscopy of aqueous solutions: Streaming potentials of NaX (X = Cl, Br, and I) solutions and electron binding energies of liquid water and X−

The streaming potentials of liquid beams of aqueous NaCl, NaBr, and NaI solutions are measured using soft X-ray, He(I), and laser multiphoton ionization photoelectron spectroscopy. Gaseous molecules are ionized in the vicinity of liquid beams and the photoelectron energy shifts are measured as a function of the distance between the ionization point and the liquid beam. The streaming potentials change their polarity with concentration of electrolytes, from which the singular points of concentration eliminating the streaming potentials are determined. The streaming currents measured in air also vanish at these concentrations. The electron binding energies of liquid water and I(-), Br(-), and Cl(-) anions are revisited and determined more accurately than in previous studies.

Study of ultrafast dynamics of 2-picoline by time-resolved photoelectron imaging.

The dynamics of electronically excited states in 2-picoline is studied using femtosecond time-resolved photoelectron imaging spectroscopy. The internal conversion from the S(2) state to the vibrationally excited S(1) state is observed in real time. The secondarily populated high vibronic S(1) state deactivates further to the S(0) state. Photoelectron energy and angular distributions reveal the feature of ionization from the singlet 3p Rydberg states. In addition, variation of time-dependent anisotropy parameters indicates the rotational coherence of the molecule.

Real-time observation of cascaded electronic relaxation processes in p-Fluorotoluene

Ultrafast electronic relaxation processes following two photoexcitation of 400nm in p-Fluorotoluene (pFT) have been investigated utilizing time-resolved photoelectron imaging coupled with time-resolved mass spectroscopy. Cascaded electronic relaxation processes started from the electronically excited S2 state are directly imaged in real time and well characterized by two distinct time constants of ~85±10fs and 2.4±0.3ps. The rapid component corresponds to the lifetime of the initially excited S2 state, including the structure relaxation from the Franck-Condon region to the conical intersection of S2/S1 and the subsequent internal conversion to the highly excited S1 state. While, the slower relaxation constant is attributed to the further internal conversion to the high levels of S0 from the secondarily populated S1 locating in the channel three region. Moreover, dynamical differences with benzene and toluene of analogous structures, including, specifically, the slightly slower relaxation rate of S2 and the evidently faster decay of S1, are also presented and tentatively interpreted as the substituent effects. In addition, photoelectron kinetic energy and angular distributions reveal the feature of accidental resonances with low-lying Rydberg states (the 3p, 4s and 4p states) during the multi-photon ionization process, providing totally unexpected but very interesting information for pFT.

Superexcited State Dynamics of OCS: An Experimental Identification of Three Competing Decay-Channels Among Autoionization, Internal Conversion and Neutral Predissociation

The 7sσ and 6pσ superexcited Rydberg states of OCS belonging to series converging onto the B̃2Σ+ ionic limit have been successfully prepared by three-photon UV excitation, and their ensuing competing relaxation processes have been probed by a time-delayed IR ionization pulse. The time profiles of S+ ions, which encode their fragmentation mechanism, are only observable at high pump intensities, thus providing unique experimental identification of the neutral predissociation channel producing S* atoms. Benefiting from this feature and by comparison with the time behavior of OCS+ ions, three competing relaxation channels are identified: autoionization associated with both X̃2Π and Ã2Π ionic states; internal conversion to isoenergetic RA states, the deactivation of which manifests as a picosecond decay in the time profile of OCS+ ions; picosecond neutral predissociation appearing as a nondecaying plateau in the time profiles of S+ ions.

Third-order optical nonlinearities of TiO2/PS composite system

A TiO2/PS composite system is prepared by chemical vapor deposition which is a common technique in preparation of nano-materials. We report the measurements of the nonlinear refractive index of the TiO2/PS composite system as measured by the reflection Z-scan technique. The large magnitude of the third-order nonlinear coefficients of the TiO2/PS composite system shows that it is a promising candidate for further material development and possible photonic device applications.

Studies of Ultrafast Dynamics of 3-Picoline with Femtosecond Time-Resolved Photoelectron Imaging

The ultrafast dynamics of excited states in 3-picoline was studied using femtosecond time-resolved photoelectron imaging, coupled with time-resolved mass spectroscopy. An ultrafast internal conversion from the S-2 state to the vibrationally excited S-1 state in about 910 fs was observed. This secondary-populated S-1 state further deactivates to the S-0 state in 2.77 ps. The photoelectron energy and angular distributions show ionizations from the singlet 3p Rydberg states. Two 400 nm photon excitations to the 3s Rydberg state suggest that this state probably decays to the ground state in 62 fs.

Ultrafast Internal Conversion Dynamics of 2-Chloropyridine by Femtosecond Time-Resolved Photoelectron Imaging

Ultrafast internal conversion dynamics of 2-chloropyridine were studied by femtosecond time-resolved photoelectron imaging spectroscopy coupled with time-resolved mass spectroscopy. The ultrafast internal conversion from the second excited state (S-2) to the first excited state (S-1) via an adjacent conical intersection within (162 +/- 5) fs was clearly observed from the time-dependence of the photoelectron spectra. The subsequent deactivations involved the coupling of S-2/S-0 (the ground state) and S-1/S-0 conical intersections, which occurred on a timescale of about (5.5 +/- 0.3) ps, and led to the internal conversion to the ground state from the S-2 and S-1 states.