Few-photon single ionization of cold rubidium in the over-the-barrier regime

Photoionization of the rubidium (Rb) atoms cooled in a magneto-optical trap, characterized by the coexistence of the ground 5$S_{1/2}$ and the excited 5$P_{3/2}$ states, is investigated experimentally and theoretically with the 400 nm femtosecond laser pulses at intensities of $I=3\times10^9$ W/cm$^2$ - $4.5\times10^{12}$ W/cm$^2$. Recoil-ion momentum distribution (RIMD) of Rb$^+$ exhibits rich ring-like structures and their energies correspond to one-photon ionization of the 5$P_{3/2}$ state, two-photon and three-photon ionizations of the 5$S_{1/2}$ state, respectively. With the increasing of $I$, we find that experimental signals near zero-momentum (NZM) in RIMDs resulted from the 5$P_{3/2}$ state enhance dramatically and its peaked Rb$^+$ momenta dwindle obviously while that from the 5$S_{1/2}$ state is maintained. Meanwhile, the ion-yield ratio of the 5$S_{1/2}$ over the 5$P_{3/2}$ states varies from $I$ to $I^{1.5}$ as $I$ increases. These features indicate a transition from perturbative ionization to strong-perturbative ionization for the 5$P_{3/2}$ state. Numerical simulations by solving the time-dependent Schr\"odinger equation (TDSE) can qualitatively explain the measurements of RIMD, photoion angular distributions, as well as ion-yield ratio. However, some discrepancies still exist, especially for the NZM dip, which could stem from the electron-electron correlation that is neglected in the present TDSE simulations since we have adopted the single-active-electron approximation

Making medicines more accessible in China: An empirical study investigating the early progress of essential medicine system

<div><p>Objective</p><p>To assess changes in medicine availability and prices as well as subsequent affordability during the early years of the National Essential Medicine System (NEMS) reform in China.</p><p>Methods</p><p>Data were obtained from four provinces through a field survey conducted in 2010–2011. Outcome measures were percentage availability, delivery efficiency, ratios of local prices to international reference prices (MPRs), and number of days’ household income needed to purchase medicines. Prices were adjusted for inflation/deflation and purchasing power parity.</p><p>Results</p><p>Under NEMS, the median MPR for essential medicines decreased from 3.27 times to 1.59 times from 2009 to 2010. The median medicine expenditure under standard treatments in 2010 equaled 1.06 days household income at a low-income level and 0.25 days household income at a middle-income level. A 25.67% reduction was observed in the average number of medicines stocked by primary healthcare facilities in 2011 compared with 2009 and the availability of essential medicines was 66.83%. During 2009–2011, suppliers could respond to 98.24% of the purchasing orders raised by primary healthcare facilities, and 89.32% of the order amounts could be delivered.</p><p>Conclusions</p><p>The market prices of essential medicines greatly decreased in China after the establishment of NEMS and showed improved affordability in the short term. However, current medicine prices remain high compared to international reference prices. Medicines were often unaffordable for economically backward residents. Future policies still need to target medicine availability as well as affordability.</p></div

The median price ratios for essential medicines before and after NEMS in four provinces.

<p>The median price ratios for essential medicines before and after NEMS in four provinces.</p

The quantity of medicines stocked by primary healthcare centers, 2009–2011.

<p>The quantity of medicines stocked by primary healthcare centers, 2009–2011.</p

The median price ratios for essential medicines before and after NEMS.

<p>The median price ratios for essential medicines before and after NEMS.</p

The affordability of medicines before and after NEMS.

<p>The affordability of medicines before and after NEMS.</p

The quantity and distribution of PHCs in the field survey.

<p>The quantity and distribution of PHCs in the field survey.</p

The availability of essential medicines in PHCs from 2009 to 2011.

<p>The availability of essential medicines in PHCs from 2009 to 2011.</p

The efficiency of medicine delivery from 2009 to 2011.

<p>The efficiency of medicine delivery from 2009 to 2011.</p

Manipulating coupling state and magnetism of Mn-doped ZnO nanocrystals by changing the coordination environment of Mn via hydrogen annealing

Mn-doped ZnO nanocrystals are synthesized by a wet chemical route and treated in H2/Ar atmosphere with different H2/Ar ratios. It is found that hydrogen annealing could change the coordination environment of Mn in ZnO lattice and manipulate the magnetic properties of Mn-doped ZnO. Mn ions initially enter into interstitial sites and a Mn3+O6 octahedral coordination is produced in the prepared Mn-doped ZnO sample, in which the nearest neighbor Mn3+ and O2 ions could form a Mn3+-O2--Mn3+ complex. After H2 annealing, interstitial Mn ions can substitute for Zn to generate the Mn2+O4 tetrahedral coordination in the nanocrystals, in which neighboring Mn2+ ions and H atoms could form a Mn2+-O2--Mn2+ complex and Mn-H-Mn bridge structure. The magnetic measurement of the as-prepared sample shows room temperature paramagnetic behavior due to the Mn3+-O2--Mn3+ complex, while the annealed samples exhibit their ferromagnetism, which originates from the Mn-H-Mn bridge structure and the Mn-Mn exchange interaction in the Mn2+-O2--Mn2+ complex