Upper limits for interstellar fulvene and nitric acid.

Radio searches for the 1 oi-0oo transition of fulvene (an isomer of benzene) at 6399 MHz and for the 1io-1ii transition of nitric acid at 5839 MHz were not successful. Upper limits are reported for fulvene against three galactic sources and for nitric acid against four. Our measurements indicate that nitric acid may be underabundant with respect to cyanoacetylene in the direction of Sgr B2. Subject headings: interstellar matter - molecules, interstellar - radio lines