Laser schlieren measurement of vibrational relaxation times for N2O in mixtures containing CO, N2, and Ar behind a shock wave

1984 ◽  
Vol 27 (11) ◽  
pp. 911-914
Author(s):  
A. P. Zuev ◽  
S. S. Negodyaev ◽  
B. K. Tkachenko
Keyword(s):  
Shock Wave ◽  
Vibrational Relaxation ◽  
Relaxation Times

The Master Equation for the Dissociation of a Dilute Diatomic Gas IX. Rotation–Vibration Relaxation Times

1973 ◽  
Vol 51 (12) ◽  
pp. 1923-1932 ◽  
Author(s):  
E. Kamaratos ◽  
H. O. Pritchard
Keyword(s):  
Shock Wave ◽  
Relaxation Time ◽  
Vibrational Relaxation ◽  
Transition Probabilities ◽  
Transition Probability ◽  
Relaxation Times ◽  
Rotational Relaxation ◽  
Relaxation Matrix ◽  
Coupling Case ◽  
Increasing Temperature

The relationships between individual rotational or vibrational transition probabilities and the eigenvalues of the 172nd order relaxation matrix describing the rotation–vibration–dissociation coupling of ortho-hydrogen are explored numerically. The simple proportionality between certain transition probabilities and certain eigenvalues, which was found previously in the vibration–dissociation coupling case, breaks down. However, it is shown that at 2000°K the second smallest eigenvalue of the relaxation matrix (dn−2), hitherto regarded as determining the "vibrational" relaxation time, is related more to the transition probability assigned to the largest rotational gap which lies in the first (ν = 0 ↔ ν = 1) vibrational gap, i.e. to the transition ν = 0, J = 5 ↔ ν = 0, J = 7, than to anything else; this clearly supports an earlier suggestion that the transient which immediately precedes dissociation in a shock wave has to be regarded as a rotation–vibration relaxation time rather than a vibrational relaxation time. It is suggested that the Lambert–Salter relationships can be rationalized on this assumption.An analysis is then made of the energy uptake associated with each eigenvalue at three temperatures. At 500°K, the greatest energy increment is associated with two eigenvalues (dn−13 and dn−24) and can be characterized as essentially a rotational relaxation: the calculations confirm that the observed rotational relaxation time should first decrease and then increase with increasing temperature, as was recently found to be the case experimentally. At 2000°K, large energy increments are associated with several eigenvalues between dn−2 and dn−14, and at 5000°K, with most of the eigenvalues dn−2 to dn−23; thus, the higher the temperature, the more complex is the (T–VR) rotation–vibration relaxation. Further, relaxation times for the same temperature measured by ultrasonic and shock-wave techniques need not agree.

On the interpretation of measured rotational and vibrational relaxation times. II. Sudden change experiments

1976 ◽  
Vol 54 (15) ◽  
pp. 2372-2379 ◽  
Author(s):  
Huw Owen Pritchard
Keyword(s):  
Shock Wave ◽  
Relaxation Time ◽  
Vibrational Relaxation ◽  
Normal Mode Analysis ◽  
Relaxation Times ◽  
Sudden Change ◽  
Heat Bath ◽  
Mode Analysis ◽  
Wave Excitation ◽  
Measured Relaxation

This paper examines, in terms of the normal-mode analysis developed earlier (Part I), the nature of relaxations in which a diatomic gas, highly diluted in a heat bath of inert gas atoms, is subjected to a sudden change as in shock-wave excitation or laser schlieren experiments.It is shown in detail how the observed relaxation time in a shock-wave excitation to a fixed final temperature depends on the initial temperature. At the same time, it is confirmed that the characterisation as 'mainly rotational' of the measured relaxation time in H2 when it is heated from room temperature to 1500 K in a shock wave is perfectly plausible.On the other hand, the calculations show that in laser schlieren experiments in which the v = 1, J = 1 level of H2 is overpopulated, the vibrational relaxation time of H2 at the temperature in question is recovered, although interesting effects should appear if other J levels were populated initially, or if the experiments were carried out at much higher ambient temperatures.The calculations also demonstrate that it is not generally possible to derive relaxation times by following the variation in population of any particular level of the molecule: multiple overshoots sometimes occur, and apparent relaxation times both longer or shorter than the true relaxation times could often result from attempts to follow level populations as a function of time.

Vibrational Relaxation Times in Oxygen

1959 ◽  
Vol 30 (6) ◽  
pp. 1614-1615 ◽  
Author(s):  
Morris Salkoff ◽  
Ernest Bauer
Keyword(s):  
Vibrational Relaxation ◽  
Relaxation Times

Vibrational Relaxation Times in Nitrogen

1957 ◽  
Vol 27 (5) ◽  
pp. 1149-1155 ◽  
Author(s):  
S. J. Lukasik ◽  
J. E. Young
Keyword(s):  
Vibrational Relaxation ◽  
Relaxation Times

Vibrational Relaxation Times in Gases

1950 ◽  
Vol 21 (12) ◽  
pp. 1319-1325 ◽  
Author(s):  
Wayland Griffith
Keyword(s):  
Vibrational Relaxation ◽  
Relaxation Times
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