Subject: Re: CCL:Temperature Calculations

From: "Dr. Heinz Schiffer" <[email-masked]>
Date: Fri, 04 Apr 1997 08:53:34 +0200

M.Govender wrote:
> 
> Dear Netters,
> 
> I am interested in obtaining Rotational and Vibrational
> temperature calculations on spherical top molecules. Can anyone
> provide any info as to what programs are available?...
> 
> Many Thanks
> Magan

Hi Magan,

Look at Donald A. McQuarrie, Statistical Mechanics, Harper & Row 1976.
All the relevant formulars are there. The vibrational temperature
of the normal frequency nu_j is 

	Theta_nu_j = h * nu_j / k
 
The rotational temperatures of a general polyatomic molecule are :

	Theta_A = A / k
	Theta_B = B / k
	Theta_C = C / k

A, B, and C are the rotational constants in Joule. Normally they
are given in cm**(-1), that is as A_quer = A / ( h * c ). A, B, and
C are defined as 

	A = h**2 / ( 8 * pi**2 * I_A )
	B = h**2 / ( 8 * pi**2 * I_B )
	C = h**2 / ( 8 * pi**2 * I_C )

I_A, I_B, and I_C are the principle moments of inertia. You can get 
them by diagonalizing the moments of inertia tensor. The formalas in
the McQuarrie book on page 134 are wrong : I_xy is missing a negative
sign : I_xy = - sum_j .... and in the formulas for A_quer, B_quer, and
C_quer the pi should be squared, see above.

Ciao,
Heinz	
-- 
Dr. Heinz Schiffer		Phone   ++49-69-305-2330
Hoechst CR&T			Fax     ++49-69-305-81162
Scientific Computing, G864	Email   [email-masked]
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