Room-temperature ordered photon emission from multiexciton states in single CdSe core-shell nanocrystals

We report room-temperature ordered multiphoton emission from multiexciton states of single CdSe(CdZnS) core(-shell) colloidal nanocrystals (NCs) that are synthesized by wet chemical methods. Spectrally and temporally resolved measurements of biexciton and triexciton emission from single NCs are also presented. A simple four level system models the results accurately and provides estimates for biexciton and triexciton radiative lifetimes and quantum yields.     

High resolution FTIR spectroscopy of pentafluoroethane: perturbations in the Coriolis doublet of ν4 and ν13

The FTIR spectrum of pentafluoroethane (R125) was measured in the mid infrared region from 900 to 4000 cm⁻¹. Vibrational assignments for R125 are revised by comparison of previous and current experimental data with ab initio calculations at both the MP2/6-311+(d,p) and B3LYP/TZV+(3df,3p) levels of theory. High resolution FTIR spectra were recorded at room temperature and in an enclosive flow cell at a rotational temperature of 140 K. The cold spectrum was sufficiently resolved to enable rovibrational analyses of the overlapping ν₄ (1200.7341 cm⁻¹) and ν₁₃ (1223.3 cm⁻¹) bands, which have a/c hybrid and b-type character, respectively. Ground state combination differences were used to confirm assignment of 2375 lines to ν₄ (J_max = 86, K_{a max} = 50) and 2921 lines to ν₁₃ (J_max = 60, K_{a max} = 54). Effective rotational and centrifugal distortion constants were determined for ν₄, and the polarization ratio was found to be . Severe Coriolis perturbations prevent any satisfactory fit to the ν₁₃ band.     

Kinetics of water-assisted single-walled carbon nanotube synthesis revealed by a time-evolution analysis

Here we investigate the kinetics of water-assisted CVD (henceforth denoted as supergrowth CVD) by a quantitative time-evolution analysis based on a simple growth model. We found that the supergrowth can be well described by a model where the dynamics of the catalyst activity is treated similar to radioactive decay. An in-depth analysis based on this growth model revealed the kinetics of the supergrowth CVD, showing a scale relationship between the carbon source and water, and elucidated the role of water as a catalyst activity enhancer and preserver.     

Novel synthetic approach to the 8,10-dimethyl anti-syn-anti-perhydrophenanthrene skeleton

[reaction: see text] An efficient and highly stereocontrolled approach to the 8,10-dimethyl anti-syn-anti-perhydrophenanthrene carbon skeleton starting with the Wieland-Miescher ketone is described. The approach centers on a Diels-Alder-angular methylation-deoxygenation sequence.     

Crossing Probabilities and Modular Forms

We examine crossing probabilities and free energies for conformally invariant critical 2-D systems in rectangular geometries, derived via conformal field theory and Stochastic Löwner Evolution methods. These quantities are shown to exhibit interesting modular behavior, although the physical meaning of modular transformations in this context is not clear. We show that in many cases these functions are completely characterized by very simple transformation properties. In particular, Cardy's function for the percolation crossing probability (including the conformal dimension 1/3), follows from a simple modular argument. A new type of higher-order modular form arises and its properties are discussed briefly.     

On λ-Fold Equipartite Oberwolfach Problem with Uniform Table Sizes

We consider the following generalization of the Oberwolfach problem:”At a gathering there are n delegations each having m people. Is it possible to arrange a seating of mn people present at s round tables T ₁, T ₂, . . . , T _s (where each T _i can accommodate \( t_i\geq3 \) people and \( \sum t_i = mn \)) for k different meals so that each person has every other person not in the same delegation for a neighbor exactly λ times?” For λ= 1, Liu has obtained the complete solution to the problem when all tables accommodate the same number t of people. In this paper, we give the completesolution to the problem for \( \lambda\geq2 \) when all tables have uniform sizes t.     

Double-charge-exchange and inelastic scattering in π−+3He

The reactions π^?+³He→⁺+3n and π^?+³He→^?+³He were studied to investigate the $\text{T=}\text{3}\text{2}$ three-nucleon system. The differential cross sections were measured at scattering angles from 20 to 40 degrees. The secondary pion was momentum analyzed in a magnetostrictive-readout wire-chamber spectrometer. The double-charge-exchange reaction yielded a secondary pion energy distribution, the features of which can be due to either a $\text{T=}\text{3}\text{2}$ three-nucleon resonance or a resonace of the nucleons in the ³He nucleus. The inelasticc scaterring reaction yielded a secondary pion energy distribution peaked near threshold, consistent with resonances in both the $\text{T=}\text{3}\text{2}$ and $\text{T=}\text{1}\text{2}$ three-nucleon systems.