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[UDUNITS #MZJ-180852]: udunits question molecules/cm^2

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  • Subject: [UDUNITS #MZJ-180852]: udunits question molecules/cm^2
  • Date: Wed, 11 May 2011 15:49:34 -0600
James,

> If I have a variable and the units are molecules/cm^2 is it acceptable to
> enter the units as molecules/cm2, that seems to be what comment 2. says below.
> But running udunits2 with molecules/cm2 says 'Don't recognize "molecule/cm2"'.
> Entering just cm-2 for units seems a bit vague and non-specific compared to
> molecules/cm2.
> 
> 
> <unit>
> <!--
> 
> 1. The mole is the amount of substance of a system which contains
> as many elementary entities as there are atoms in 0.012 kilogram of
> carbon 12.
> 
> 2. When the mole is used, the elementary entities must be specified
> and may be atoms, molecules, ions, electrons, other particles, or
> specified groups of such particles.
> 
> -->
> <base/>
> <name>
> <singular>mole</singular>
> </name>
> <symbol>mol</symbol>
> </unit>
> <unit>

You should use the unit "1/cm2".

The UDUNITS package won't understand the unit "molecule/cm2".

Attaching additional meaning to a unit string (e.g., "molecule") is considered 
bad form. See section 7.4 at <http://physics.nist.gov/Pubs/SP811/sec07.html>. 
The proper place to put such information is in the name of the physical 
quantity.

> ------------------------------------------------------------------------------
> | James E. Johnson                      | address:                           |
> | Wyle Information Systems, Inc.        |  NASA Goddard Space Flight Center  |
> | e-mail: address@hidden        |  Distributed Active Archive Center |
> | phone:  301-614-5121                  |  Code 610.2, Bldg 32, Room S130G   |
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> ------------------------------------------------------------------------------

Regards,
Steve Emmerson

Ticket Details
===================
Ticket ID: MZJ-180852
Department: Support UDUNITS
Priority: Normal
Status: Closed