Dry excited singlet delta oxygen generator

An improved method and apparatus for producing dry excited singlet delta oxygen for use in iodine lasers.

This invention relates to lasers and, more particularly, to an improved 
apparatus for generating dry excited singlet delta oxygen used in the 
operation of iodine lasers. There has recently been emerging an increased 
interest in continuous wave (CW) iodine chemical lasers. The wave length 
of the laser transition (1315.2 nanometers) lies in a region of favorable 
atmospheric transmission. Further, the energy source for the laser, being 
completely chemical, requires no significant external sources of power. 
Since the energy transfer rate dominates all quenching rates in the system 
(including the reverse pumping reaction), gas phase mixing problems are 
minimized; and the conditions essential for operation at greater than 100 
torr pressure exist. Finally, this laser represents the first of a class 
of chemically pumped electronic transition lasers, any of which could be 
of great interest for future development. 
These chemically pumped iodine lasers utilize singlet delta oxygen which 
has been produced heretofore by a hetrogenous gas/liquid phase reaction 
which produces molecular oxygen in the singlet delta state. This species 
acts as an energy transfer agent to pump the .sup.2 P.sub.1/2-.sup.2 
P.sub.3/2 spin orbit transition of atomic iodine. The singlet delta oxygen 
generator provides the major portion of the mass flow of the chemical 
laser. Thus, an efficient, high yield generator is essential for the 
effective operation of such a laser at high output powers. The chemical 
reaction commonly used in the prior art to produce singlet delta oxygen is 
a hypochlorite H.sub.2 O.sub.2 reaction. The overall stoichoimetry of the 
reaction is given by 
EQU H.sub.2 O.sub.2 +Cl.sub.2 +NaOH.fwdarw.O.sub.2 (a.sup.1 
.DELTA.g)+NaCl+HCl+H.sub.2 O. 
The reaction is produced by bubbling chlorine gas through a hydrogen 
peroxide-sodium hydroxide mixture. Unfortunately, because of the large 
quantities of foam which develop during the course of this reaction there 
is a substantial limitation upon the flow rate of chlorine and, 
accordingly, upon the rate of singlet delta oxygen produced. 
In accordance with this invention, a novel apparatus and method for 
producing dry excited singlet delta oxygen are provided. Nitrogen is 
utilized as a carrier gas to allow high total pressure operation of the 
device. A mixture of hydrogen peroxide and potassium hydroxide (or other 
hydroxides such as sodium hydroxide, cesium hydroxide, or calcium 
hydroxide) is sprayed under pressure against a jet of gaseous chlorine to 
produce a fine spray of liquid droplets surrounded by chlorine gas. By the 
above described reaction, a mixture of singlet delta excited oxygen and 
salt water (H.sub.2 O and KCl) is produced in nitrogen gas along with 
traces of initial and intermediate reactants. 
The mixture is carried to the inlet of a rotating or static centrifugal 
separator wherein the water droplets are removed from the gaseous stream. 
The nitrogen and excited oxygen then flow to the inlet of a freezing 
section to remove any remaining water vapor. The resultant product is a 
gas comprising as its principal constituents, singlet delta oxygen and the 
carrier gas nitrogen. This may then be transferred for reaction in the 
iodine laser without interference from the nitrogen gas which is inert.

Referring now to the drawing, a singlet delta oxygen generator 10 is 
contained in a suitable housing 12 which may be a conduit connecting a 
source of nitrogen gas 14 and an iodine laser 16. Of course, it will be 
readily understood that the oxygen generator 10 may be utilized in any 
circumstances where a source of singlet delta oxygen is required. The flow 
of nitrogen from the source 14 is maintained at a pressure of up to one 
atmosphere throughout the process of oxygen generation. 
A mixture of hydrogen peroxide and potassium hydroxide in liquid form is 
sent through a conduit 18 to a nozzle 20 for injection into the flow of 
nitrogen gas in the generator 10. In the preferred embodiment, the liquid 
contains, on a molar basis, about 9.33 percent hydrogen peroxide and 18.67 
percent potassium hydroxide and 72 percent water. However, other 
hydroxides, such as sodium hydroxide, cesium hydroxide, calcium hydroxide 
and others may be used as alternatives to potassium hydroxide where 
desirable. 
Chlorine gas is fed through a conduit 22 into a jet 24 interposed directly 
ahead of nozzle 20 such that the mixture of hydrogen peroxide and 
potassium hydroxide is sprayed under pressure against the gaseous chlorine 
flow to produce a fine spray of liquid droplets surrounded by chlorine 
gas. The liquid mixture and chlorine react by the reaction: 
EQU H.sub.2 O.sub.2 +Cl.sub.2 +KOH.fwdarw.O.sub.2 (a.sup.1 
.DELTA.g)+KCl+HCl+H.sub.2 O 
to produce a mixture of singlet delta excited oxygen and salt water 
(H.sub.2 O+KCl) in the nitrogen gas. In addition, traces of the initial 
reaction as well as intermediate reactants of the chemical reactants will 
be found in the nitrogen gas stream. Unlike previous systems wherein 
chlorine was bubbled through vats of the liquid mixture, no foam develops 
in the generator 10. Thus, the consumption rate of chemicals is limited 
only by the physical configuration of the generator 10. 
The wet mixture is then carried by the flow of nitrogen gas to the inlet of 
a rotating centrifugal separator 26. In the separator, the water droplets 
are forced to the outer diameter of the rotating drum forming the 
principal component of the separator. The droplets coalesce to form a 
rotating film of liquid which flows along the surface of the drum, driven 
by the gas flow, until it is driven radially into a toroidal collector 28 
from which the fluid is directed through a tube 30 for disposal. 
The nitrogen and excited oxygen flow along the separator to the inlet of a 
freezing section 32 which is preferably one pass of a heat exchanger, the 
other pass of which is connected to a source of liquid nitrogen through a 
conduit 34. In the freezing section, substantially all of the water vapor 
remaining in the flowing gas is removed. 
At the outlet of the freezing section 32, a mixture of gases exists 
consisting of up to 50 torr of total oxygen (having more than 50 percent 
singlet delta oxygen), less than 20 torr of initial and intermediate 
reactants, less than 1 torr of water and the balance of nitrogen. 
In this manner, a generator is provided which can produce singlet delta 
oxygen in any suitable quantities required without the problems 
encountered in the prior art chlorine bubbling type systems. It should be 
noted that the production of liquid droplets in fine spray may be 
accomplished in a variety of ways, for example, by use of commercial blend 
fuel injectors commonly used in gas turbine combustion chambers or by fuel 
injectors commonly used in oil furnaces. 
While the Applicant has endeavored to set forth the preferred embodiment of 
practicing the invention, the scope of the invention should not be limited 
by the specification but only by the scope of the following claims.