Clearification on technical resignation from Central Government to State Government

Sir, I am a Central Govt. employee and completed 9 yrs of service as on date 13/09/2019 in the rank of Constable. Now I had been selected for the post of Sub-Inspector in West Bengal Police under West Bengal State Government for which I already took proper permission from my Department. Does my resignation may be considered as technical resignation and my past services and pensionary benefit may also carry forward in new Department. Kindly provide legal aid in this regard please.