Chemical Physics
This year, JILA celebrates its 60th anniversary. Officially established on April 13, 1962, as a joint institution between the University of Colorado Boulder and the National Institute of Standards and Technology (NIST), JILA has become a world leader in physics research. Its rich history includes three Nobel laureates, groundbreaking work in laser development, atomic clocks, underlying dedication to precision measurement, and even competitive sports leagues. The process of creating this science goliath was not always straightforward and took the dedication and hard work of many individuals.
In a new paper published in the Journal of Physical Chemistry Letters, Jimenez and his team report a new experimental setup to search for the cause of a mysterious fluorescent signal that appears to be from entangled photon excitation. The results of their new experiments suggested that hot-band absorption (HBA) by the subject molecules, could be the potential culprit for this mysterious fluorescent signal, making it the prime suspect.
Breath analysis has been fast progressing in recent years and is continuing to gain more and more research interest. It is, however, experimentally challenging due to the extremely low concentrations of molecules present in each breath, limited number of detectable molecular species, and the long data-analysis time required. Now, a JILA-based collaboration between the labs of NIST Fellows Jun Ye and David Nesbitt has resulted in a more robust and precise breath-testing apparatus. In combining a special type of laser with a mirrored cavity, the team of researchers was able to precisely measure four molecules in human breath at unprecedented sensitivity levels, with the promise of measuring many more types of molecules.
The basic question of how strands of nucleic acids (DNA and RNA) fold and hybridize has been studied thoroughly by biophysicists around the globe. In particular, there can be unexpected challenges in obtaining accurate kinetic data when studying the physics of how DNA and RNA fold and unfold at the single molecule level. One problem comes from temporal camera blur, as the cameras used to capture single photons emitted by these molecules do so in a finite time window that can blur the image and thereby skew the kinetics. In a paper published in the Journal of Physical Chemistry B, JILA Fellow David Nesbitt, and first author David Nicholson, propose an extremely simple yet broadly effective way to overcome this camera blur.
Most researchers would agree that it is much easier to write a paper about an observed effect than a paper proving the nonexistence of the effect when it is not observed. NIST JILA Fellow Ralph Jimenez found this to be the case in contributing to a recent paper published in Physical Review Applied. The authors of this paper were originally hoping to observe the increased efficiency in two-photon absorption, a special type of process used in microscopy of living tissue, that had been reported by other research labs. This increased efficiency would be determined by an additional absorption signal than the one being produced by classical light. This additional signal came from using entangled photons. Instead, Jimenez and his team of collaborators from NIST found no additional signal in their measurements, indicating a lack of absorption entirely from the entangled photons.
When it comes to chemical reactions, shape matters. The Lewandowski Group have studied acetylene and its reactions with propyne and allene to find out how an isomer changes the chemical reaction pathway.
The Weber Group has found what causes rubrene to generate upconversion photoluminescence. By exploring new routes to triplet formation and triplet-triplet annihilation, they learn how organic materials can take lower-energy photons and generate higher energy output, which could have implications for photovoltaics and new electronics.
Fluorescence and dyes are great tools to study cells, proteins, bacteria, or DNA. But scientists need to efficiently sort out the glowing material from the non-glowing stuff in their samples. The Jimenez Lab and the JILA Electronics Shop teamed up to create an improved flow cytometry system which can not only sort fluorescent material faster, it can sort by fluorescence lifetime and brightness faster than a commercially available system.
Dr. Thomas Perkins won a Gears of Government Award for his work in atomic force microscopy.
JILA researchers have created a laser-controlled "electron faucet", which emits a stable stream of low-energy electrons. These faucets have many applications for ultrafast switches and ultrafast electron imaging. The electron faucet starts with gold, spherical nanoshells.