scholarly journals Detectors for fast time-resolved studies at SSRC, status and future

2020 ◽  
Author(s):  
L. I. Shekhtman ◽  
A. S. Arakcheev ◽  
V. M. Aulchenko ◽  
V. N. Kudryavtsev ◽  
V. D. Kutovenko ◽  
...  
Keyword(s):  
Fast Time ◽  
Time Resolved

The dynamics of the reaction of O(1D) with HBr studied by crossed molecular beams and time-resolved Fourier transform spectroscopy

1994 ◽  
Vol 72 (3) ◽  
pp. 888-902 ◽  
Author(s):  
N. Balucani ◽  
L. Beneventi ◽  
P. Casavecchia ◽  
G. G. Volpi ◽  
E. J. Kruus ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Large Fraction ◽  
Branching Ratio ◽  
Molecular Beams ◽  
Momentum Conservation ◽  
Fourier Transform Spectroscopy ◽  
Fast Time ◽  
Time Resolved ◽  
Vibrational Distribution ◽  
Crossed Molecular Beams

The reaction O(1D) + HBr has been investigated by the crossed molecular beams and infrared chemiluminescence methods in an effort to characterize the dynamics of both possible reactive channels. The angular and velocity distribution of the BrO product from the O(1D) + HBr → BrO + H pathway have been obtained in crossed beam experiments at collision energies, Ec, of 5.0 and 14.0 kcal/mol. The product center-of-mass angular distribution is found to be almost backward–forward symmetric at both Ec, with backward scattering being slightly favored, from which it is deduced that two processes contribute to this channel: a dominant one occurring via formation of a long-lived complex, following O(1D) insertion, and another one occurring via direct abstraction of the halogen atom and giving rise to a rebound dynamics. The large fraction (≈50%) of available energy released into translation indicates the existence of a potential barrier for H-displacement in the exit channel. From energy and angular momentum conservation arguments, it is inferred that BrO is formed rotationally very hot in the lowest vibrational levels of both 2Π3/2 and 2Π1/2 electronic states. The initial vibrational distribution of the OH product from the O(1D) + HBr → OH + Br channel has been measured using fast time-resolved Fourier transform spectroscopy. The vibrational distribution is strongly inverted, from which it is deduced that the HOBr intermediate dissociates very rapidly, before energy randomization occurs. A lower limit to the branching ratio of the relative cross sections for the BrO + H and OH + Br channels is derived (σ(BrO + H)/σ(OH + Br) ≥ 0.16 ± 0.07) and compared to recent bulk work. The dynamical results for the overall reaction are discussed with reference to the relevant singlet and triplet potential energy surfaces and possible molecular configurations involved. Comparison with the dynamics of the ground state reaction O(3P) + HBr → OH + Br is carried out also, to examine the effect of electronic excitation on the dynamics of the reactions of atomic oxygen with hydrogen halides.

Time-Resolved Micro-Raman Thermometry for Microsystems in Motion

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Justin R. Serrano ◽  
Sean P. Kearney
Keyword(s):  
Microelectromechanical Systems ◽  
Diagnostic Technique ◽  
Temperature Measurements ◽  
Transient Temperature ◽  
Raman Signal ◽  
Periodic Signal ◽  
Fast Time ◽  
Time Resolved ◽  
Microelectromechanical Devices ◽  
Reliable Temperature

Micro-Raman thermometry has been demonstrated to be a feasible technique for obtaining surface temperatures with micron-scale spatial resolution for microelectronic and microelectromechanical systems (MEMSs). However, the intensity of the Raman signal emerging from the probed device is very low and imposes a requirement of prolonged data collection times in order to obtain reliable temperature information. This characteristic currently limits Raman thermometry to steady-state conditions and thereby prevents temperature measurements of transient and fast time-scale events. In this paper, we discuss the extension of the micro-Raman thermometry diagnostic technique to obtain transient temperature measurements on microelectromechanical devices with 100 μs temporal resolution. Through the use of a phase-locked technique we are able to obtain temperature measurements on electrically powered MEMS actuators powered with a periodic signal. Furthermore, we demonstrate a way of obtaining reliable temperature measurements on micron-scale devices that undergo mechanical movement during the device operation.

scholarly journals Time-Resolved Infrared Spectroscopy in Supercritical Fluids

1999 ◽  
Vol 19 (1-4) ◽  
pp. 133-139 ◽  
Author(s):  
Michael W. George ◽  
Martyn Poliakoff ◽  
Xue-Zhong Sun ◽  
David C. Grills
Keyword(s):  
Infrared Spectroscopy ◽  
Supercritical Fluids ◽  
Room Temperature ◽  
Noble Gas ◽  
Fast Time ◽  
Metal Carbonyls ◽  
Time Resolved ◽  
Organometallic Reactions ◽  
Time Resolved Infrared Spectroscopy ◽  
First Time

We have used fast Time-resolved Infrared Spectroscopy (TRIR) to probe organometallic reactions in supercritical fluids on the nanosecond time-scale. This has allowed us to identify, for the first time in solution at room temperature, organometallic noble gas complexes which are formed following irradiation of metal carbonyls in supercritical noble gas solution. We have found that these complexes are surprisingly stable and have comparable reactivity to organometallic alkane complexes. We have also studied the coordination of CO2 to metal centres in supercritical CO2 (scCO2) and provide the first evidence for the formation and reactivity of ɳ1-O bound metal CO2 complexes in solution at or above room temperature.

Ultra-fast Time-Resolved Electron Diffraction of Strongly Driven Phase Transitions on Silicon Surfaces

2009 ◽  
Vol 1230 ◽  
Author(s):  
Simone Möllenbeck ◽  
Anja Hanisch-Blicharski ◽  
Paul Schneider ◽  
Manuel Ligges ◽  
Ping Zhou ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Electron Diffraction ◽  
Structural Phase ◽  
High Energy ◽  
Silicon Surfaces ◽  
Fast Time ◽  
Time Resolved ◽  
Disorder Phase Transition ◽  
Pulse Pump

AbstractThe dynamics of strongly driven phase transitions at surfaces are studied by ultra-fast time-resolved reflection high energy electron diffraction. The surfaces are excited by an intense fs-laser pulse (pump) and probed by an ultra-short electron pulse with variable time delay. The order-disorder phase transition from a c(4×2) to a (2×1) of the bare Si(001) surface shows a transient decrease of the intensity of the c(4×2) spots which recovers on a time scale of a few hundred picoseconds indicating the excitation of the phase transition. On Si(111) a monolayer of Indium induces a (4×1) reconstruction which undergoes a Peierls like phase transition to a (8ד2”) reconstruction below 100 K. Upon laser excitation at a temperature of 40 K the phase transition was strongly driven. The (8ד2”)-diffraction spots instantaneously disappears, while the intensity of the (4×1)-spots increases. This increase of the (4×1) spot intensity excludes an explanation by the Debye-Waller-Effect and is evidence for a true structural phase transition at a surface.

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