What Can We Infer About the Isospin of an Alpha Particle?

[dudu1]

I am reading Griffiths' introduction to elementary particles and I am confused about problem 4.33a in that book.

It says that given there is no isotope of hydrogen of weight 4, nor of lithium of weight 4, what can we say about the isospin of an alpha particle?

Thanks in advance!

 

[Meir Achuz]

The Ispin of the alpha (He^4) is zero. If it were one, then there would be Li^4 and H^4
patners.