22 CFR §19.11-3

1. (a)In the absence of a joint election or a spousal agreement to the contrary, a participant or former participant who is separated from active service on or after February 15, 1981 who is married at the commencement of his/her annuity shall provide a regular survivor annuity for a spouse under § 19.10-2 equal to the maximum amount that remains available under limitations stated in paragraph (b) of that section after allowing for any commitment of a regular survivor annuity for a former spouse who has not remarried prior to age 60 and who is alive on the date the former participant becomes eligible for an annuity.
2. (b)A regular survivor annuity is also payable to a surviving spouse for whom a principal elected an annuity under § 19.10-3, § 19.10-4, or § 19.11-2(c) following a marriage after comencement of his/her annuity.
3. (c)The amount of a regular survivor annuity equals 55 percent of the base designated for the benefit at the time the principal's annuity commenced, adjusted by the total percentage of cost-of-living increases the principal was receiving at death.
4. (d)A survivor annuity is payable to a surviving spouse only if that person was married to the principal at the time of his/her death or if the spouse became a former spouse under the definition in § 19.2(k).