Jianbing Qi

Photoassociative Production and Trapping of Ultracold KRb Molecules

We have produced ultracold heteronuclear KRb molecules by the process of photoassociation in a two-species magneto-optical trap. Following decay of the photoassociated KRb*, the molecules are detected using two-photon ionization and time-of-flight mass spectroscopy of KRb+. A portion of the metastable triplet molecules thus formed are magnetically trapped. Photoassociative spectra down to 91 cm(-1) below the K(4s)+Rb(5p(1/2)) asymptote have been obtained. We have made assignments to all eight of the attractive Hunds case (c) KRb* potential curves in this spectral region.

High resolution spectroscopy and channel-coupling treatment of the A 1Σ+–b 3Π complex of NaRb

The paper presents the study of the fully mixed Au200a1Σ+–bu200a3Π complex of the NaRb molecule based on high-resolution sub-Doppler spectroscopy and intensity measurements, ab initio relativistic calculations of energies, transition moments and spin–orbit interactions, as well as an inverted channel-coupling approach (ICCA) deperturbation analysis. A two-laser V-type pump–probe excitation scheme was employed to obtain A←X transition frequencies to 16 A-state vibrational levels from v=6 to v=21 with J from 8 to 23. Additionally, relative intensities in laser-induced A→X fluorescence spectra have been recorded, including progressions with all observable transitions to the ground state vibronic levels, the latter yielding unambiguous v assignment of the A-state levels observed. All experimental rovibronic term values and all measured intensity distributions were embedded in a direct simultaneous weighted nonlinear fitting in the framework of an elaborated ICCA allowing us to obtain deperturbed relativistic diabatic...

Formation, detection and spectroscopy of ultracold Rb2 in the ground X1Σg+ state

We form ultracold ground-state Rb2 molecules by photoassociating pairs of atoms in a magneto-optical trap into the 0u+ state, which decays radiatively into high vibrational levels of the X1Σg+ state. Sensitive and vibrationally state-selective detection is achieved by means of resonantly-enhanced two-photon ionization with a pulsed laser. Frequency scans of the detection laser reveal a long vibrational progression to a previously unobserved electronic excited state, which we identify as the 21Σu+ state. Most of its vibrational spectrum is in excellent agreement with predictions based on ab initio potentials, although the lowest vibrational levels exhibit strong perturbative mixing with the triplet 23Πu state. The detection method reported here, with minor variations, should be effective for the entire potential well of the X state. In this work no transitions are observed from vibrational levels above v = 118, but this turns out to be a limitation not of the detection method but rather of the photoassociative formation scheme, due to re-excitation of the highest-v levels by the same photoassociation laser that produces them.

Photoassociation of 85Rb atoms into 0u+ states near the 5S+5P atomic limits

New photoassociation data on the 0u+ levels of Rb2 below the 5S+5P1/2 limit are combined with older data (Cline et al 1994 Phys. Rev. Lett. 73 632) in a fit to potentials and spin–orbit functions. The P1/2 data exhibit oscillations in the B(v) values due to coupling between the two 0u+ series, as modelled accurately by a coupled potentials approach. The fitted value for the C3 dispersion parameter from the combined data agrees well with the value derived from the pure long-range 0g− state.

Formation, Detection and Trapping of Photoassociated Ultracold KRb Molecules

Ultracold ground-state KRb molecules are formed by photoassociation and detected by resonant two-photon ionization. We have assigned both the photoassociation spectrum and the detection laser spectrum, and we have demonstrated magnetic trapping of triplet KRb

Nucleation and growth of copper selective-area atomic layer deposition on palladium nanostructures

The nucleation and growth of copper atomic layer deposition (ALD) on palladium have been investigated for applications in nanoscale devices. Palladium nanostructures were fabricated by electron beam lithography and range in size from 250 nm to 5 μm, prepared on oxidized silicon wafers. Copper ALD using Cu(thd)2(s) and H2(g) as reactants was carried out to selectively deposit copper on palladium seeded regions to the exclusion of surrounding oxide surfaces. Nuclei sizes and densities have been quantified by scanning electron microscopy for different growth conditions. It is found that growth occurs via island growth at temperatures of 150-190 °C and alloy growth at temperatures above 210 °C. In the lower temperature window, nucleation density increases with decreasing temperature, reaching a maximum of 4.8 ± 0.2 × 109/cm2 at 150 °C, but growth is too slow for significant deposition at the lowest temperatures. At higher temperatures, individual nuclei cannot be quantified due to extensive mixing of copper and palladium layers. For the lower temperatures where nuclei can be quantified, rates of nucleation and growth are enhanced at high H2 partial pressures. At the smallest length scales, conformality of the deposited over-layers is limited by a finite nuclei density and evolving grain structure that cause distortion of the original nanostructure shape during growth.

State-selective detection of ultracold rubidium molecules in high vibrational levels of the X /sup 1//spl Sigma//sub g//sup +/ ground state

We report on state-selective detection of ultracold ground-state rubidium molecules in very high vibrational levels. Resonant two-photon ionization spectra obtained with a pulsed 600 nm laser are analyzed to identify the absolute vibrational quantum numbers.