The absorption and dispersion of ultrasonic waves in acetic acid

1949 ◽  
Vol 199 (1056) ◽  
pp. 114-130 ◽  
Keyword(s):  
Activation Energy ◽  
Acetic Acid ◽  
Relaxation Time ◽  
Wave Length ◽  
Relaxation Mechanism ◽  
Ultrasonic Waves ◽  
Ultrasonic Vibrations ◽  
Frequency Range ◽  
Velocity Of Propagation ◽  
Absorption And Dispersion

The paper gives the results of measurements of the absorption and velocity of propagation of ultrasonic waves in acetic acid over the frequency range 0.5 to 67.5 Mc./sec. and at tem­peratures from 16 to 60° C. It is shown that a dispersion and a maximum in the value of absorption per wave-length occur, and the results confirm the existence of a relaxation pro­cess arising from the perturbation of a molecular equilibrium by the ultrasonic vibrations. The absorption coefficient, α , at a frequency, v , is represented by an equation of the form α = Bv 2 + Av 2 / 1 + ( v/v m ) 2 , where A, B and v m are parameters independent of v but varying with temperature, and v m is related to the relaxation time, r , by v m = 1/2 πr . These parameters are evaluated for a series of temperatures. The results are discussed in the light of existing theory, and in particular the activation energy of the process is obtained from the measured variation of relaxation time with temperature. It is suggested that the relaxation mechanism is possibly connected with a perturbation of the equilibrium between single and double molecules of acetic acid. The results also indicate the existence of a further relaxation process giving a second maximum in the absorption per wave-length at some frequency greater than 67·5 Mc./sec.

scholarly journals Dielectric Properties of Deep Ice Cores with Air-Hydrate Inclusions (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 210
Author(s):  
Shinji Mae ◽  
Takeo Hondoh ◽  
Masayoshi Nakawo ◽  
C.C. Langway
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Dielectric Properties ◽  
Time Variation ◽  
Volume Fraction ◽  
Ice Cores ◽  
Frequency Range ◽  
Temperature Range ◽  
The Core

Air-hydrate inclusions have been found in deep ice cores from Dye 3, Greenland, which were taken in August 1981. Although the concentration of the air-hydrate crystals decreased with time, when the core was stored at a temperature of −50 °C, they still existed to an appreciable extent in 1985. An ice specimen was cut out from the Dye 3 core at a depth of 1500 m, where the volume fraction of the hydrate crystals was about 10−3 by volume. Its dielectric properties were measured in September 1985, in a frequency range of 30-20 × 103 Hz and temperature range of −20° to −90°C. The activation energy obtained for the relaxation time of the Debye dispersion was about 0.2 eV, which is much smaller than that of pure ice. The measurement was repeated once a month for about a year, and the sample was stored at a temperature of −10 °C between measurements. The time variation of the dielectric properties has been discussed in relation to the deterioration of the air-hydrate crystals.

Ultrasonic relaxation processes in liquid triethylamine

1956 ◽  
Vol 237 (1209) ◽  
pp. 233-244 ◽  
Keyword(s):  
Activation Energy ◽  
Energy Barrier ◽  
Ultrasonic Waves ◽  
Relaxation Processes ◽  
Activation Energy Barrier ◽  
Temperature Range ◽  
Rotational Isomers ◽  
Velocity Of Propagation ◽  
Ultrasonic Relaxation ◽  
The Difference

Measurements have been made of the velocity of propagation and the absorption of ultrasonic waves in liquid triethylamine over the temperature range 25 to 70° C and at frequencies of approximately 23, 66, 107, 148 and 192 Mc/s. The absorption results demonstrate the existence of a relaxation process which is attributed to the perturbation by the sound wave of an equilibrium between rotational isomers. The activation energy barrier and the difference in energy between the states are evaluated from an analysis of the results. The calculated dispersion of velocity is less than 1%. Values of the specific heat of triethvlamine are required in the analysis and are given in the paper for the temperature range 25 to 60°C. The results are discussed in the light of other measurements concerned with rotational isomers.

Ultrasonic measurements and the second viscosity of carbon disulphide

1954 ◽  
Vol 226 (1164) ◽  
pp. 51-51 ◽  
Keyword(s):  
Relaxation Time ◽  
Carbon Disulphide ◽  
Wave Length ◽  
Relaxation Times ◽  
Adiabatic Compressibility ◽  
Ultrasonic Waves ◽  
Appreciable Effect ◽  
Ultrasonic Absorption ◽  
Low Frequencies ◽  
Ultrasonic Measurements

In a previous paper (Andreae & Lamb 1951) the ultrasonic absorption in a liquid was deduced thermodynamically, starting from an expansion of the adiabatic compressibility. This procedure has been revised, using a more satisfactory expansion, and a general expression is derived for the absorption due to a single relaxing process. The relaxation time ז a of a mechanism A , giving rise to a dispersion of the ultrasonic waves in the neighbourhood of a frequency f a , is assumed to be much less than, or much greater than, the relaxation times of all other processes occurring within the liquid. It is then found that processes having a much smaller relaxation time than ז a may have an appreciable effect on calculations of the absorption per wave-length due to mechanism A . Experimental measurements are presented which delineate a dispersion in carbon disulphide centred around 75 Mc/s at 25° C and 31 Mc/s at -63° C. The dispersion is attributed to a relaxation of the total vibrational specified heat. The absence of any dispersion at low frequencies can be inferred from static com­pressibility data.

Absorption and Dispersion of Ultrasonic Waves in Acetic Acid

Nature ◽  
1948 ◽  
Vol 162 (4130) ◽  
pp. 993-994 ◽  
Author(s):  
JOHN LAMB ◽  
J. H. ANDREAE ◽  
R. BIRD
Keyword(s):  
Acetic Acid ◽  
Ultrasonic Waves ◽  
Absorption And Dispersion

scholarly journals Dielectric Properties of Deep Ice Cores with Air-Hydrate Inclusions (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 210-210
Author(s):  
Shinji Mae ◽  
Takeo Hondoh ◽  
Masayoshi Nakawo ◽  
C.C. Langway
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Dielectric Properties ◽  
Time Variation ◽  
Volume Fraction ◽  
Ice Cores ◽  
Frequency Range ◽  
Temperature Range ◽  
The Core

Air-hydrate inclusions have been found in deep ice cores from Dye 3, Greenland, which were taken in August 1981. Although the concentration of the air-hydrate crystals decreased with time, when the core was stored at a temperature of −50 °C, they still existed to an appreciable extent in 1985.An ice specimen was cut out from the Dye 3 core at a depth of 1500 m, where the volume fraction of the hydrate crystals was about 10−3 by volume. Its dielectric properties were measured in September 1985, in a frequency range of 30-20 × 103 Hz and temperature range of −20° to −90°C. The activation energy obtained for the relaxation time of the Debye dispersion was about 0.2 eV, which is much smaller than that of pure ice.The measurement was repeated once a month for about a year, and the sample was stored at a temperature of −10 °C between measurements. The time variation of the dielectric properties has been discussed in relation to the deterioration of the air-hydrate crystals.

Correlating Blocking Temperatures in Single Molecule Magnets with Raman Relaxation

2018 ◽  
Author(s):  
Marcus J. Giansiracusa ◽  
Andreas Kostopoulos ◽  
George F. S. Whitehead ◽  
David Collison ◽  
Floriana Tuna ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Single Molecule ◽  
Energy Barrier ◽  
Thermal Relaxation ◽  
Relaxation Mechanism ◽  
Blocking Temperature ◽  
Single Molecule Magnets ◽  
Single Molecule Magnet ◽  
Key Parameter

We report a six coordinate DyIII single-molecule magnet<br>(SMM) with an energy barrier of 1110 K for thermal relaxation of<br>magnetization. The sample shows no retention of magnetization<br>even at 2 K and this led us to find a good correlation between the<br>blocking temperature and the Raman relaxation regime for SMMs.<br>The key parameter is the relaxation time (𝜏<sub>switch</sub>) at the point where<br>the Raman relaxation mechanism becomes more important than<br>Orbach.

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