Expert: Jayendra Upadhye - 9/29/2005

Question
In astronomy, a "singly ionized" gas is a gas in which just one electron has been removed from every atom, "doubly ionized" refers to the removeal of two electrons from every atom, and so on. which of the following gasses would not be able to creat any spectral line pattern when heated?
a)singly ionized hydrogen
b)singly ionized helium
c)doubly ionized carbon
d)doubly ionized oxygen
e)all of the above would be able to creat spectral line patterns. Any gas that is heated to sufficiently high temperatures will do this.

Answer
Hi,
Field theory suggests that electrons only fall into stable orbits where the length of the orbit is integeral multiples of h/(2*pi).

when an atom absorbs a photon, an electron jumps from one quantum energy level to another where the difference accounts for energy absorbed from the incoming photon.

since E = h * frequency, (h is planck's constant), this absorbed enrrgy leads to absorption of all photons of light corresponding to that energy level.Leading to an absorption line characteristic of that element / compound.

when the electron EMITS light and goes back to its natural state, that is equivalent to emitting a photon with frequency that is again governed by E = h * frequency. That is our emission spectrum.
Again charcteristic for each element / compound

all gases can thus emit and absorb photons no matter whether they are ionised or not.

Truly any gas that is heated sufficiently will do that. As in order to have emission spectra, al one needs is hot (rarified) gas with enough electrons in excited states.

this site explains the spectra well:-
http://www.pas.rochester.edu/~blackman/ast104/absorption.html

this site actually tells how noble gases at room temperature actually emitted IR spectrum when bombarded with 5 MeV proton beam!

(only in place of photons, particles were used to agitate electrons in the gas indirectly by first freeing some electrons and these in turn bump into and excite some of the neutral gas into emitting IR light!).
http://www.pd.infn.it/~conti/ired.html
hope that answers your query.
Jayen