No abstract

High-resolution laser-induced fluorescence spectroscopy has been used to investigate the 18 163 cm Ϫ1 band of Pt 2 in a supersonically cooled molecular beam. Rotational constants of the ground and excited states were extracted from the rotationally resolved spectrum and determined to be B 0 Љ ϭ0.031 754(12) cm Ϫ1 and B 0 Јϭ0.028 672(11) cm Ϫ1 , respectively. These values correspond to ground-and excited-state bond lengths of r 0 Љϭ2.33297(44) Å and r 0 Јϭ2.455 16(47) Å, respectively. Nuclear spin statistics that are observed in the spectrum demonstrate that the ground state is of either 0 g ϩ or 0 u Ϫ symmetry. Of these, 0 g ϩ is by far the more probable. Comparisons with Au 2 are made, suggesting that it may be appropriate to consider Pt 2 as having a double bond.

It is presumed that heat generated from a trigger cell under thermal runaway (TR) in multi-cell Li-ion batteries is transferred to adjacent cells mostly by convection of ejected hot matter (and to a lesser degree by direct contact and radiative heat transfer). Therefore, venting the energized materials (ejecta) from the battery compartment should prevent cell-to-cell TR propagation. However, engineering solutions to vent ejecta from TR of an individual cell fail to prevent TR propagation, subsequently causing battery fires. Real-time in situ FTIR spectroscopy of ejecta from a cell driven into TR demonstrates that large amounts of carbonate esters are already vented from the cell before it goes into TR. The vented hot gases cool down and condense on top of adjacent cells. Subsequently, when the trigger cell reaches TR, this condensate ignites, transferring heat and potentially driving the receiving cells into TR. Computational fluid dynamics and thermal simulations of this pathway support the experimental findings. Numerical results indicate that a fraction of the solvent vented from the trigger cell is sufficient for efficient TR propagation. Our results shed new light on thermal propagation in multi-cell Li-ion batteries and suggest novel methods to prevent TR propagation.

A 150 km free-space optical (FSO) communication link between Maui (Haleakala) and Hawaii (Mauna Loa) was demonstrated by JHU/APL and AOptix Technologies, Inc. in September 2006. Over a 5 day period, multiple configurations including single channel 2.5 Gbps transmission, single channel 10 Gbps, and four wavelength division multiplexed (WDM) 10 Gbps channels for an aggregate data rate of 40 Gbps were demonstrated. Links at data rates from 10 to 40 Gb/s were run in excess of 3 contiguous hours. Data on the received power, frame synchronization losses, and bit error rate were recorded. This paper will report on the data transfer performance (bit error rates, frame synchronization issues) of this link over a 5 day period. A micropulse lidar was run concurrently, and on a parallel path with the FSO link, recording data on scattering loss and visibility. Comparisons between the state of the link due to weather and the data transfer performance will be described.

No abstract