High-resolution infrared spectroscopy of acetylenic compounds: Vibrational dynamics in the fundamental and first overtone of the acetylenic C-H stretch

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:5649496

Pate, B H

The author has measured the high resolution infrared spectra of a number of acetylenic compounds in the collimated molecular beam, optothermal spectrometer. The unique advantages of bolometer detection have allowed him to measure not only the acetylenic C-H stretch fundamentals but also the first overtones. Resolution in the fundamental is about 8 MHz and in the overtone it is about 16 MHz. He has used the spectrometer to study a series of symmetric top terminal actylenes of increasing size. He has observed spectra that are characteristic of the three regimes of intramolecular vibrational energy redistribution (IVR): sparse, intermediate, and statistical. For both intermediate and statistical case spectra he is able to obtain homogeneous lifetime data that measures the time scale for energy localization in the acetylenic C-H bond. The author has used the ability to determine IVR lifetimes to study the effects of structural modifications on the IVR rate in similar molecules. In one case he has found that the substitution of a heavier atom into the central position of trimethyl acetylenic compounds results in slower IVR rates. The rates he has measured have all been extraordinarily long, ranging up to about 6 ns. Interestingly, the longest lifetimes have been measured in the largest molecules he has studied and in the overtone region. He has also considered the effects of changing the identity of internal rotors in the substituted acetylenes. Again he finds that structural changes greatly affect the IVR rate. For example, methyl group deuteration of tertbutylacetylene increases the IVR rate by a factor of five. In both cases he has attempted to interpret these results in the context of existing theories. However, he found that these theories cannot fully explain the rate data.

• Research Organization: Princeton Univ., NJ (United States)
• OSTI ID: 5649496
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
664000 -- Atomic & Molecular Physics-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ACETYLENE
ALKYNES
BEAMS
BOLOMETERS
CHEMICAL BONDS
ENERGY LEVELS
EXCITED STATES
HYDROCARBONS
INFRARED SPECTRA
MEASURING INSTRUMENTS
MOLECULAR BEAMS
ORGANIC COMPOUNDS
SPECTRA
STRUCTURAL CHEMICAL ANALYSIS
VIBRATIONAL STATES