Closed form solution for Helmholtz equation $(\Delta + 1) p(x) = 0$ in free space?

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Consider the Helmholtz equation

$$(\Delta + 1) p(x) = 0 \quad \quad x \in \mathbb{R}^2$$

with the Sommerfield radiation condition applying to $p$. That is,

$$\lim_{|x| \to \infty} \bigg(\frac{\partial}{\partial |x|} - i \bigg) p(x) = 0.$$

Is a straightforward closed form analytic solution possible for this problem?