Particle $\mathrm{A}$ of mass ${\mathrm{m}}_1$ moving with velocity $\left(\sqrt{3}\hat{\mathrm{i}}+\hat{\mathrm{j}}\right){\mathrm{ms}}^{-1}$ collides with another particle $\mathrm{B}$ of mass ${\mathrm{m}}_2$ which is at rest initially. Let ${\overrightarrow{\mathrm{v}}}_1$ and ${\overrightarrow{\mathrm{v}}}_2$ be the velocities of particles $\mathrm{A}$ and $\mathrm{B}$ after collision respectively. If ${\mathrm{m}}_1=2{\mathrm{m}}_2$ and after collision ${\overrightarrow{\mathrm{v}}}_1-\left(\hat{\mathrm{i}}+\sqrt{3}\hat{\mathrm{j}}\right){\mathrm{ms}}^{-1}$, the angle between ${\overrightarrow{\mathrm{v}}}_1$ and ${\overrightarrow{\mathrm{v}}}_2$ is :