THE SEARCH FOR EXTRAGALACTIC LITHIUM HYDRIDE

We have conducted Combined Array for Research in Millimeter-wave Astronomy observations of LiH, in absorption, toward three quasars. These quasars, B0218+357, PKS1830–211, and PKS0201+113, have redshifts of z = 0.685 – 3.387, and shift the LiH J = 1-0 transition to the 1 mm and 3 mm wavelength bands, where atmospheric absorption is sharply reduced from that predominating near the rest frequency of 443 GHz. We report a 3σ detection of LiH toward B0218+357 with a column density of 1.4 × 1012 cm–2 and place an upper limit on the 6Li/7Li ratio of <0.16. LiH was not detected toward any other source.