Silver halide emulsion and silver halide photographic lightsensitive material

A silver halide emulsion having been chemically sensitized by at least one compound selected from the following four types of electron-releasing compounds:

• (Type 1) an electron-releasing compound capable of undergoing a one-electron oxidation to thereby form a one-electron oxidation product thereof, the one-electron oxidation product capable of releasing further two or more electrons accompanying a subsequent bond cleavage reaction;
• (Type 2) an electron-releasing compound capable of undergoing a one-electron oxidation to thereby form a one-electron oxidation product thereof, the one-electron oxidation product capable of releasing further one electron accompanying a subsequent bond cleavage reaction, and the one-electron oxidation product having, in its molecule, two or more adsorptive groups acting on silver halides;
• (Type 3) an electron-releasing compound capable of undergoing a one-electron oxidation to thereby form a one-electron oxidation product thereof, the one-electron oxidation product capable of releasing further one or more electrons after going through a subsequent bond forming process;
• and
• (Type 4) an electron-releasing compound capable of undergoing a one-electron oxidation to thereby form a one-electron oxidation product thereof, the one-electron oxidation product capable of releasing further one or more electrons after going through a subsequent intramolecular ring cleavage reaction.