, Please 
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First we open the image the image that will be converted to infrared mode. It is important that this is image that has lot of sunshined surface. Autumn time with lot of newborn plants and bluming trees are the best object for infrared images.
We then make the copy of layer1 with Layer -->Duplicate layer --> OK.
we must open afterwards Image -->Adjustments --> Channel Mixer...
We check Monochrone, and then push slider for Red color to 200%, slider for Green to -40% and slider for Blue to -60%. Important thing is that sum of red, green and blue is 100% (R200%-G40%-B60%=100%) Click OK.
We select upper layer named "Background copy", make right click -->Blending options -->Opacity -->80% -->OK. We decided to use opacity cause we want to have a bit of information on colours of original picture. So opacity will make layer of Background copy a bit transperent.
Click for enlarged final result
We save image afterwards in desired picture format and enjoying in our first digital infrared (IR) picture. I never have tried what image would have looked like if I used actual infrared filter. But from what I see this is giving good results anyway.
A word on channel mixer. Wherever you will decide to make your images IR look, this values will not be correct for every specific image, so R200% is a starter, then we must decide about values on other two colors, this is G and B.
Here is result with mixing values of R=-42%, G=200% and B=-58%.
But I doubt it will suceed in your way. Or maybe I am wrong? Cause you are changing colours in this option and IR is functioning like this. 
